Forensic Science International

Forensic Science International is an international journal publishing original contributions in the many different scie...

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Forensic Science International is an international journal publishing original contributions in the many different scientific disciplines pertaining to the forensic sciences. Fields include forensic pathology and histochemistry, chemistry, biochemistry and toxicology (including drugs, alcohol, etc.), biology (including the identification of hairs and fibres), serology, odontology, psychiatry, anthropology, the physical sciences, firearms, and document examination, as well as investigations of value to public health in its broadest sense, and the important marginal area where science and medicine interact with the law. Review Articles and Preliminary Communications (where brief accounts of important new work may be announced with less delay than is inevitable with major papers) may be accepted after correspondence with the appropriate Editor. Case Reports will be accepted only if they contain some important new information for the readers. Submission of Articles: Manuscripts prepared in accordance with Instructions to Authors should be sent to the Editor-in-Chief or one of the Associate Editors according to their area of expertise as listed below. If there is any doubt, a preliminary letter, telefax or telephone enquiry should be made to the Editor-in-Chief or his Assistant.

EDITOR-IN-CHIEF P. Saukko – (for: Experimental Forensic Pathology, Traffic Medicine and subjects not listed elsewhere) Department of Forensic Medicine, University of Turku, SF-20520 Turku, Finland Tel.: (+358) 2 3337543; Fax: (+358) 2 3337600; E-mail: [email protected]

SECRETARY TO THE EDITOR-IN-CHIEF A. Saarenpää – Address as for P. Saukko. Tel: (+358) 2 3337438; Fax: (+358) 2 3337600; E-Mail: [email protected]

ASSOCIATE EDITORS A. Carracedo – ( for: Forensic Genetics) Instituto de Medicina Legal, Facultad de Medicina, 15705 Santiago de Compostela, Galicia, Spain Fax: (+34) 981 580336 O.H. Drummer – ( for: Toxicology) Department of Forensic Medicine, Victorian Institute of Forensic Medicine 57–83 Kavanagh Street, Southbank 3006, Victoria, Australia Tel.: (+61)-3-9684-4334; Fax: (+61)-3-9682-7353

P. Margot – (for: Questioned Documents, with the assistance of A. Khanmy and W. Mazzela; and for Physical Science: ballistics, tool marks, contact traces, drugs analysis, fingerprints and identification, etc.) Ecole de Sciences Criminelles (ESC), UNIL-BCH, CH-1015 Lausanne, Switzerland Fax: (+41) 21 692 4605 G. Willems – ( for: Odontology) Katholieke Universiteit Leuven, School of Dentistry, Oral Pathology and Maxillo-Facial Surgery, Departments of Orthodontics and Forensic Odontology, Kapucijnenvoer 7, B-3000 Leuven, Belgium Tel: +32 16 33.24.59; Fax: +32 16 33.24.35

Cristina Cattaneo – ( Anthropology and Osteology) Instituto de Medicina Legal, Università degli Studi Via Mangiagalli 37, 20133 Milano, Italy Tel: 0039 2 5031 5678; Fax: 0039 2 5031 5724

EDITORIAL BOARD A. Amorim (Porto, Portugal) J. Buckleton (Auckland, New Zealand) B. Budowle (Quantico, VA, USA) J. Clement (Melbourne, Australia) S.D. Cohle (Grand Rapids, MI, USA) S. Cordner (South Melbourne, Australia) P. Dickens (Buxton, UK) M. Durigon (Garches, France) A. Eriksson (Umeä, Sweden) J.A.J. Ferris (Auckland, New Zealand) M.C. Fishbein (Encino, USA) P. Gill (Solihull, UK) C. Henssge (Essen, Germany) M.A. Huestis (Baltimore, MD, USA)

A.W. Jones (Linköping, Sweden) H. Kalimo (Helsinki, Finland) B. Kneubuehl (Thun, Switzerland) S. Leadbeatter (Cardiff, UK) P.J. Lincoln (Surrey, UK) A. Luna Maldonado (Espinardo (Murcia), Spain) B. Madea (Bonn, Germany) N. Morling (Copenhagen, Denmark) B. Olaisen (Oslo, Norway) V. Pascali (Rome, Italy) S. Pollak (Freiburg i. Br., Germany) M.S. Pollanen (Toronto, Canada) D. Pounder (Dundee, UK) O. Prokop (Berlin, Germany)

K. Püschel (Hamburg, Germany) G. Quatrehomme (Nice, France) J. Robertson (Canberra, Australia) P.M. Schneider (Cologne, Germany) S. Seta (Tokyo, Japan) J. Simonsen (Copenhagen, Denmark) P. Sótonyi (Budapest, Hungary) M. Steyn (Pretoria, South Africa) F. Tagliaro (Verona, Italy) T. Takatori (Chiba, Japan) S. Tsunenari (Kumamoto, Japan) D.N. Vieira (Coimbra, Portugal) X. Xu (Shantou, People’s Republic of China) J. Zhu (Guangzhou, People’s Republic of China)

Forensic Science International 166 (2007) 85–90 www.elsevier.com/locate/forsciint

Lethal paradoxical cerebral vein thrombosis due to suspicious anticoagulant rodenticide intoxication with chlorophacinone F. Papin a, F. Clarot b,*, C. Vicomte b, J.M. Gaulier c, C. Daubin d, F. Chapon e, E. Vaz b, B. Proust b a Forensic Department, Caen University Hospital, Caen, France Medical Forensic Institute, Rouen University Hospital, Charles Nicolle, Rouen, France c Pharmacokinetic and Toxicology Laboratory, Limoges University Hospital, Limoges, France d Intensive Care Unit, Caen University Hospital, Caen, France e Neuropathology Department, Caen University Hospital, Caen, France b

Received 9 February 2006; received in revised form 4 April 2006; accepted 9 April 2006 Available online 23 May 2006

Abstract Superwarfarin exposure is a growing health problem, described in many countries. The authors report a case of suspicious chlorophacinone poisoning with a problematic diagnosis. They review the literature and discuss particularities of anticoagulant rodenticide intoxication, as well as the apparent contradiction between anticoagulant intoxication and lethal thrombosis. # 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Rodenticide; Chlorophacinone; Poisoning; Anticoagulant; Cerebral vein thrombosis

1. Introduction Rodenticide intoxication is rare, as these products are no longer used as rodenticide due to its hazardous effects on humans. Nevertheless, these products may still be found in certain garden sheds, and could have a ‘‘criminal’’ use. The authors report a case of suspicious chlorophacinone poisoning with a problematic diagnosis. Particularities of anticoagulant rodenticide intoxication are discussed; usefulness of blood analysis in suspected poisoning or intoxication is underlined. The authors also discuss the physiopathological characteristics of their case, as well as the apparent contradiction between anticoagulant intoxication and lethal thrombosis. 2. Case report A 34-year old woman, farm worker, with no particular previous medical history or medication – with the exception of * Correspondence to: Institut de Me´decine Le´gale, CHU Rouen, Charles Nicolle, 76031 Rouen Cedex, France. Tel.: +33 232888284; fax: +33 232888367. E-mail address: [email protected] (F. Clarot). 0379-0738/$ – see front matter # 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.forsciint.2006.04.003

an oral oestroprogestative contraception – presented in the emergency department with a massive hematuria. On admission, the patient was apyretic and physical examination confirmed macroscopic hematuria and had abdominal pain in the right hypochondral region, which initially occurred 3 days earlier. No particular violence related lesion was observed. The patient was initially treated by analgesics and intravenous NSAIDs. Blood laboratory tests revealed a hyperleucocytosis (12,500/ 3 mm) which resulted in antibiotic treatment and hospitalization for suspected infected renal colitis. The following day, abdominal ultrasonography was performed and revealed pyelo-calicis hyperechogenicity with no dilatation. Moreover, a slight fluid collection was observed medially to the right kidney, and a mobile echogenic residue was also found in the bladder. The patient continued to have pain and hematuria, and at day 4 she suddenly presented convulsive loss of consciousness. She was transferred to the intensive care unit in a comatose state (Glasgow scale 4) and was then sedated, intubated, and ventilated. Initial neurological examination showed hypotonic coma, a non-reactive left mydriasis and rapidly bilateral areactive mydriasis. She was administered 100 mg of mannitol and a CT

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F. Papin et al. / Forensic Science International 166 (2007) 85–90

Fig. 1. Initial CT scan show a large left hemisphere haemorrhagic cerebral infarct, a diffuse oedema, a subarachnoid haemorrhage, and a right shifting of the midline structure with a left ventricule disappearance.

scan was performed with no contrast agent (Fig. 1). It revealed an extended left hemisphere haemorrhagic cerebral infarct, associated with diffuse oedema and midline structure shifted to the right. Biological screening revealed a slight anemia (10.3 g/ dl), an increased hyperleucocytosis (19,490/3 mm) and a normal platelet count. Coagulation study showed an unexplained very low prothrombin time (10%) and especially very low levels of Vitamin K dependant factors (II, VII, IX, and X). However, antithrombin III and factor V were normal. Cerebral angiography, performed to assess the brain perfusion state, revealed a thrombosis of the superior longitudinal sinus (SLS) (Fig. 2). Despite intravenous Vitamin K injection and adapted resuscitation, our patient died in an irreversible comatose state, at day 4.

Further subsequent toxicological analysis performed on a serum sample collected during hospitalization, the 4th day before the death, revealed a high level of chlorophacinone: 25.9 mg/L. At autopsy, performed 4 days after death, we found a slight nail and lip cyanosis, pulmonary asphyxia lesion, and a trachea oedema. Moreover, autopsy revealed diffuse haemorrhagic signs (i.e. multiple ecchymosis, visceral haemorrhages, pleural and peritoneal blood collection, diffuse subarachnoid haemorrhage, and renal intracavity haemorrhage). The biological samples collected were sent to the laboratory for forensic toxicological analysis. Macroscopic and histologic examination confirmed a bilateral and diffuse alveolar pulmonary oedema, a multivisceral congestion, and demonstrated a concentric myocardial hypertrophy. Neuropathological examination confirmed SLS thrombosis. It also showed a left frontal region haemorrhagic infarct lesion, a diffuse oedema, and herniation of the fifth temporal circumvolution (Fig. 3). Police investigation was not able to assess the origin of the intoxication, which was not considered as criminal, but accidental or suicidal. 3. Materials and methods Venous blood sample was collected during hospitalization, the fourth day before the death. Initially, blood was taken to perform coagulation tests but extensive toxicological screening (including a chlorophacinone assay) was subsequently performed in a serum sample, due to the diagnostic problems, using high-performance liquid chromatography coupled with diode-array detection (HPLC– DAD). A second toxicological investigations set was performed in a forensic context 4 days after death, on autopsy biological samples (peripheric blood, urine, pleural effusion, and gastric contents). No visceral, particularly liver, analysis was performed.

Fig. 2. Cerebral angiography (via left vertebral artery) shows lack of flow of the superior longitudinal sinus and a capilar ‘‘marshy’’ stasis (left image). Lack of SLS opacification is confirmed by left lateral sinus venography (right image).


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Fig. 3. Macroscopic brain examination confirmed a left frontal haemorrhagic infarct lesion, extended to the caudate nucleus head and the corpus callosum. Examination showed as well a herniation of the 5th temporal circumvolution.

Chlorophacinone assays in serum were performed using a previously published method [1]. This analytical procedure was also applied for chlorophacinone determinations in forensic samples (i.e. blood, urine, and gastric contents) according to the results of a previous analytical validation step in such biological matrix. Briefly, this method, routinely applied for the simultaneous identification and quantitation of 13 hydroxycoumarin and indandione anticoagulant drugs [2] and rodenticides, used a reversed-phase liquid chromatography with diode-array detection technique. Extraction step consisted of an acidic and alkaline liquid–liquid double extraction with diethylether– ether acetate (50:50, v/v). High-performance liquid chromatography was performed using gradient elution with an acetonitrile and phosphate buffer on a Nucleosil C18, 5 mm particle size (150 mm 4.6 mm i.d.) column. Detection and quantitation limits for chlorophacinone were 20 and 50 mg/L, respectively. The standard calibration curve was linear from 50 to 5000 mg/L; within-run precision coefficient of variation (CV) was less than 10%, and between-run precision CV was less than 20%. Table 1 Chlorophacinone levels

Ante mortem samples Post mortem samples

Blood (mg/L)

Urine Urine (mg/L) (mg)

Gastric contents (mg/L)

Gastric contents (mg)

25.9

–

–

–

–

6.8

0.102

4.8

0.192

9.4

4. Results Toxicological screening revealed ante and post mortem high blood concentration of chlorophacinone (ante mortem toxicological screening was performed on venous peripheral blood; post mortem blood was obtain from subclavian artery). Citalopram and desmethyl diazepam were also discovered, but at therapeutic levels. Post mortem toxicological analyses were also performed in urine (15 mL) and gastric contents (40 mL); results are shown in Table 1. 5. Discussion Rodenticides are the name given to any of the group of toxic substances that are used to kill rodents. Rodenticides are a group of compounds that exhibit markedly different toxicities to humans and rodents. The varieties of rodenticides used over the years are numerous, leading to the popular expression, ‘‘to build a better mousetrap’’. Adults who ingest these substances are most likely individuals attempting suicide; however, poisoning homicides may occur with these agents due to their ready availability. Superwarfarin exposure is a growing health problem [3], described in many countries. In 2002, in U.S.A., according to the Toxic Exposure Surveillance System (TESS) of the American Association of Poison Control Centers (AAPCC), 19,674 human exposures to rodenticides have been reported. According to the 2002 TESS data, anticoagulant rodenticides were associated with 16,822 of rodenticide exposures, but only two lethal intoxications were observed [2]. These cases are

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always reported as accidental exposition, suicide attempts or Mu¨nchausen syndrome [4–8]. At the turn of the century, rodenticides were composed heavy metals such as arsenic, thallium and phosphorus along with red squill and strychnine. This changed in the 1940s as investigators discovered that warfarin could be transformed in bishydroxycoumarin when fungi in moldy sweet clover oxidize coumarin to 4-hydroxycoumarin. Warfarin was quickly adopted as the major rodenticide and in 1940, bishydroxycoumarin was synthesized and used clinically 1 year later as an oral anticoagulant under the American trade name dicumarol. However, rodents resistance to warfarin became prevalent in the 1960s via autosomal dominant gene transmittance [9]. Novel compounds were synthesized to combat rodent resistance, thereby creating a new class of anticoagulants— the superwarfarins [10]. The term superwarfarin refers to a group of compounds, second-generation anticoagulants, which are extremely longacting. These fat-soluble anticoagulants are colorless, tasteless, and odorless compounds [11]. Superwarfarins, as warfarin, inhibit hepatic synthesis of the Vitamin K-dependent coagulation factors II, VII, IX, and X and the anticoagulant proteins C and S. Chlorophacinone stops the synthesis of the active form of Vitamin K1 via inhibition of Vitamin K1–3 epoxide reductase, which blocks coagulation factor synthesis (II, VII, IX, and X) [2,9,12–16]. Superwarfarins are metabolized by hepatic cytochrome P450 isoenzymes to hydroxylated metabolites. It is uncertain that whole metabolites are inactive [9]. Chlorphacinone is an indandione-derivative with a prolonged effect of the superwarfarins family [11]. This anticoagulant is approximately 100 times more potent than warfarin on a molar basis [9]. The half-life of superwarfarin varies from 16 to 69 days compared with 37 h for warfarin [16,17]. The most human toxic form is an oily base (concentration of 2.5 g/ L), which is found in numerous commercial products worldwide. However, this form is no longer sold in France (since 2000) as it has been considered a health hazard. Each Vitamin K-dependent factor differs in its degradation half-life; factor II requires 60 h, factor VII requires 4–6 h, factor IX requires 24 h, and factor X requires 48–72 h. The half-lives of proteins C and S are approximately 8 and 30 h, respectively. As a result, because antivitamin K reduces first the activity of anticoagulant proteins C and S, a hypercoagulable state may be initially induced. Rapid loss of protein C temporarily shifts the balance in favour of clotting until sufficient time has passed for antivitamin K to decrease the activity of coagulant factors [18–21]. Chlorophacinone poisoning induces prolonged prothrombin time (PT), elevated international normalized ratio (INR), extended activated prothromboplasmin time, and decreased Vitamin K-dependent factors levels. Bleeding is the most common clinical feature and may occur from any mucosal site or organ [22–25]. The first haemorrhagic signs usually occur 3– 7 days after intake, depending on the dose ingested, and the substance half-life (from 6 to 23 days), when the body’s

reserves of prothrombin have diminished [2,4,9,12–14,26–30]. Table 2 showed 16 cases of chlorophacinone intoxication described in the literature. 5.1. Our case raises multiple problems First, concerning the origin of the intoxication, which was not (and will probably never been) assessed. Because our patient, and her family, were farm workers, they consequently had access to concentrated rodenticide for professional use. Regarding the elevated blood level of chlorophacinone, it is uncertain that intoxication involved granules, because this volume would have been too bulky to ingest. Only the oil form is known to be sufficiently concentrated to be hazardous, in small quantities, able to be ingested ‘‘accidentally’’. However, an accidental ingestion of oily chlorophacinone would suppose package reconditioning, or a severe neurological state impairment. Suicidal intoxication was considered but our patient had no previous suicidal history, nor psychiatric symptoms. Criminal poisoning was also considered, but police investigations found no arguments in favour of this hypothesis. Second, the coexistence of a haemorrhagic syndrome and an anticoagulant intoxication was initially disturbing. However, the first hypothesis considered was that SLS thrombosis occurred initially and subsequently induced neuropsychiatric impairment. Accidental or suicidal ingestion would have been consequent to these alterations. Nevertheless, our patient’s husband did not described major or sufficient behavioural abnormalities in favour of this hypothesis. In fact, the review of the literature regarding warfarin has explained this apparent contradiction [31–33]. Certain studies involved warfarin levels, monitored by measuring the prothrombin time, which responds to reductions in levels of three Vitamin K-dependent clotting factors (factors II, VII, and X). It has been demonstrated that during the first 48 h of treatment, the anticoagulant effect of warfarin is caused mainly by a reduction in the activity of factor VII, which has a half-life of 6 h. In contrast, the antithrombotic effect of warfarin (which is thought to be caused primarily by a reduction in the activity of factor II) is delayed for as long as 60 h. Therefore, during the first 48 h of therapy, the anticoagulant and antithrombotic effects of warfarin may be unrelated. In addition, because the half-life of the Vitamin K-dependent anticoagulant protein, protein C, is similar to that of factor VII, the early anticoagulant effect of warfarin (which results from reduction of factor VII) could be counteracted by a procoagulant effect (which results from reduction of protein C). Moreover, it has been also demonstrated that greater dose of warfarin was associated with a significantly more rapid decrease in protein C activity (which decreased before levels of factors X and II were substantially reduced). Therefore, the combination of markedly reduced protein C levels and near-normal levels of factors II and X over the first 2 days of warfarin therapy could produce an initial hypercoagulable state. Obviously, it is not possible to study chlorophacinone effects on humans, but it is probably scientifically possible to extrapolate warfarin data to superwarfarins.


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Table 2 Review of the literature (when chlorophacinone blood level or absoption is reported) Reference

# Case

Sex (age (years))

Intoxication reason

Death (Yes/No)

Absorption mode, dose ingested

Symptoms (appearance delay)

Biological tests (appearance delay)

Chlorophacinone blood level, half-life (Hl)

Cutaneous mucous haemorrhage (day 10) None

PT = 0%, APT = 65/32 (day 10) INR = 1.2 (hour 18)

Unknown Unknown

Haematomas, ecchymosis (day 37) None Multiple cutaneous mucous haemorrhage (day 16) Haematuria (day 15)

PT = 92% (hour 1.5)

Unknown

PT = 43% (hour 18) PT = 75% (hour 1.5); hypocoagulability (day 2) PT = 53% (a few hours later) PT = 38% (day 2) PT = 18% (day 2) PT = 65% (day 16)

Unknown Unknown

Dusein et al. [26] Murdoch et al. [30]

1

M (28)

Suicide

N

Oral, Unknown

2

F (37)

Suicide

N

Oral, 625 mg

Chataigner et al. [4]

3

F (79)

Suicide

N

Oral, 375 mg

4 5

M (45) M (18)

Suicide Suicide

N N

Oral, 500 mg Oral, 625 mg

6

M (21)

Suicide

N

Oral, 750 mg

7 8 9

M (54) M (27) M (72)

Suicide Suicide Suicide

N N N

Oral, 750 a` 1500 mg Oral, Unknown Oral, Unknown

10

M (52)

Suicide

N

Oral, 500–1200 mg

11

M (61)

Suicide

N

Oral, 500 mg

12

F (20) ans

Suicide

N

Oral, 250 mg

13

F (60) ans

Suspected suicide

N

Unknown, unknown

14

M (23) ans

Suspected suicide

N

Unknown, unknown

Arditti et al. [12]

15

F (27) ans

Suicide

N

Oral, 625 mg

Lagrange et al. [14]

16

M (33) ans

Suicide

N

Oral, 1875 mg

Burucoa et al. [9]

None None Microscopical haematuria (day 2) Haematuria, haematomas (day 2) Haematuria (day 19); gums bleeding (day 21)

Unknown Unknown Unknown Unknown

PT = 100% (a few hours later) PT < 10% (day 21)

Unknown Unknown

Lumbar pain, macroscopical haematuria (day 7) Macroscopical haematuria, vaginal bleeding, gum bleeding, thigh ecchymosis Abdominal pain, macroscopical haematuria, gum bleeding

Hypocoagulability (day 7)

Day 12: 2 mg/L, Hl: 6.5 days

Hypocoagulability

12.9 mg/L, Hl: 22.8 days

Hypocoagulability

1.2 mg/L, Hl: 11 days

Asthenia, inhalation pneumopathy (hour 80) Nausea (hour 8)

PT < 10%, APT = 44/32 (hour 80)

Hour 80: 43 mg/L, Hl: 7.6 days

PT normal (hour 8)

Hour 8: 27.6 mg/L

INR: international normalized ratio; PT: prothrombin time; APT: anti-prothrombin time.

6. Conclusion In our case, the origin of the intoxication remains unclear, and will probably never elucidated. Physicians and pathologists should bear in mind that any patient presenting with prolonged and/or unexplained hypocoagulability could have ingested superwarfarins, whether or not voluntarily. Moreover, pathologists and forensic practitioner should also keep in mind that thrombosis could paradoxically be related to anticoagulant intoxication, which is more uncommon. Acknowledgment The authors thank Richard Medeiros, Rouen University Hospital, editor, for his valuable advice in editing the manuscript.

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Detection of gunpowder stabilizers with ion mobility spectrometry C. West *, G. Baron, J.-J. Minet De´partement des Explosifs et Incendies, Laboratoire Central de la Pre´fecture de Police, 39bis rue de Dantzig, 75015 Paris, France Received 11 November 2005; received in revised form 5 April 2006; accepted 7 April 2006 Available online 7 July 2006

Abstract This study is the first reported ion mobility detection of ethyl centralite and diphenylamine (DPA) smokeless gunpowder stabilizers, together with the nitroso and nitro derivatives of diphenylamine. First, the applicability of the ion mobility spectrometry (IMS) for the substances of interest was determined. The existence of numerous peaks, both in positive and negative modes, clearly demonstrates the success of these experiments. All mono and di-nitro derivatives of DPA tested were detected with this method. Unfortunately, many of the ions generated were not accurately identified. However, reduced mobility constants representative of each ion generated under defined operating conditions could be used for purpose of compound identification. The method was then successfully tested on real gunpowder samples. By the use of IMS, we managed to establish a rapid, simple and sensitive screening method for the detection and identification of smokeless gunpowder organic components. # 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Diphenylamine; Ethylcentralite; Smokeless gunpowder; Ion mobility spectrometry (IMS)

1. Introduction Smokeless powders are commonly used in modern ammunition. Additionally, they are frequently used in the construction of improvised explosive devices (IEDs) related to criminal and terrorist acts. Therefore, in the latter case and in firearm discharge cases, the identification of some components that can associate residue samples with unfired gunpowder provides valuable evidence to the forensic scientist. When inorganic gunshot residues have not been recovered or their characteristics are non-specific, the analysis of organic residues is required to provide complementary information. The main component of smokeless gunpowder is nitrocellulose (NC). In single-based propellants, it is the only energetic material in the composition, while in double-based powders, nitroglycerin (NG) is also present. In triple-based gunpowders, other explosive components can be found, nitroguanidine being the most frequent. However, NC and NG have been regarded as being a lack of conclusive evidence [1] as NC is widely used in

* Corresponding author. E-mail addresses: [email protected] (C. West), [email protected] (J.J. Minet). 0379-0738/$ – see front matter # 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.forsciint.2006.04.004

varnishes, celluloid films and pharmaceutical industry, while NG also occurs in pharmaceutical preparations [2]. Organic additives, such as dinitrotoluene (DNT) isomers— used as a flash suppresser, dibutylphthalate—used as a plasticizer, methyl and ethyl centralite (EC) and diphenylamine (DPA)—used as stabilizers are also present in gunpowder composition. EC is regarded as a characteristic material in gunpowder but it is not present in all compositions. DPA is also commonly used in the perfumery, in the food industry and as antioxidant in the rubber and elastomer industry [3], thus, the single detection of DPA is not a diagnostic of gunpowder presence. It is well known that DPA stabilizes the energetic composition by binding nitrous oxide gases originating from NC decomposition, and converting them into stable compounds. The main reaction products of nitrous oxide gases and DPA (see Fig. 1) are N-nitroso-diphenylamine (N-NODPA), 2-nitrodiphenylamine (2-NDPA) and 4-nitrodiphenylamine (4-NDPA). N-NODPA is believed to be the primary intermediate before the nitro derivatives are formed by a Fischer–Hepp rearrangement – leading to 2-nitroso-diphenylamine (2-NODPA) and 4-nitrosodiphenylamine (4-NODPA) – and an oxidation step [4,5]. These nitroso and nitro derivatives also act as stabilizers [5,6], and

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C. West et al. / Forensic Science International 166 (2007) 91–101

Fig. 1. Dominating reaction routes of the initial DPA degradation in an aging gunpowder [4–6]. (1) DPA, (2) N-NODPA, (3) 2-NDPA, (4) 4-NODPA, (5) 4-NDPA, (6) 2-NDPA, (7) 2,4-NDPA, (8) 2,40 -NDPA.

further react with nitrous oxide gases to form highly nitrated derivatives of DPA, such as N-nitroso-2-nitro-diphenylamine (NNO-2-NDPA), 2,4-dinitrodiphenylamine (2,4-NDPA) and 2,40 dinitrodiphenylamine (2,40 -NDPA). The last compound to be formed would be the 2,20 ,4,40 ,6,60 -hexanitrodiphenylamine, that would later face decomposition into picric acid. The other origins of DPA, possibly causing environmental contamination in casework samples, can be minimized if the nitrated derivatives of DPA can also be identified in the sample, as those are unique to smokeless gunpowder. Therefore, if both energetic compounds such as NC and NG, and organic additives such as EC or DPA and some of its nitrated derivatives can be identified simultaneously in casework samples, the presence of gunpowder is ascertained. Because the amount of stabilizer initially introduced in the composition is very small (about 2%), a highly sensitive analytical method is required. The use of gas chromatography (GC) for the analysis of DPA derivatives is limited by the low volatility of the highly nitrated derivatives. Indeed, tri- and tetra-nitrodiphenylamine analogs need very high operating temperatures (up to 320 8C) [4]. GC with thermal energy analysis detection (GC–TEA) is generally prefered to GC coupled to mass spectrometry (GC–MS) as the latter is reported not to be sensitive enough for real-life samples [7]. Furthermore, N-NODPA and other nitroso derivatives of DPA are generally reported to degrade in the injection port in GC. The failure of GC to elute N-NODPA intact severely restricts its usefulness in the analysis of DPA derivatives, as N-

NODPA is the primary intermediate formed and is therefore present in high proportions. Normal phase and reversed phase high-performance liquid chromatography (HPLC) [5,8] are both commonly applied, with varied detectors: either with UV–vis spectrophotometry [9], amperometric detection [5,10], fluorimetric detection [11] or more recently with mass spectrometry [12]. HPLC leads to satisfying separations of the major nitro and nitroso derivatives. Equally good separations were reported with supercritical fluid chromatography [4,13] and micellar electrokinetic chromatography [8]. A tandem MS method was recently reported [14]. In the forensic laboratory, casework samples are often complex mixtures issued from the solvation of a complex and dirty matrix. In this case, thin layer chromatography (TLC) is the most appropriate technique. In our laboratory, we traditionally use TLC, followed by an oxidation step, for the detection of stabilizers. This method suffers from poor sensitivity and is very time consuming, but it is the most appropriate for the analysis of dirty samples. Additionally, in case studies, methods of identification based on noncorrelated separation mechanisms are needed. A method that would provide orthogonal identifications to the classical chromatographic methods is required. Thus, the combination of two such methods would enhance the identification power and the analytical reliability. Ion mobility spectrometry (IMS) is commonly used by forensic scientists to identify the major explosives, narcotics and chemical warfare agents. Basically, IMS refers to the


93

Fig. 2. Schematic representation of an IMS detector cell, adapted from ref. [21].

detection and characterization of chemical substances from their gas-phase ion mobilities at atmospheric pressure under an applied electrostatic field. The principles of IMS have been thoroughly described elsewhere [15], therefore, only a brief description of the principles of operation will be presented here. Because of its low cost of operation, fast response time (less than 10 s) and reduced sample preparation, IMS is particularly interesting as a screening technique. Amines and amides generally provide intense response with positive polarity in IMS because of high proton affinities with comparatively long-lived product ions [16]. EC is thus expected to produce positive ions. Although DPA response in positive ion mode has been reported [17,18], response of IMS towards its nitro derivatives has been unexplored. Nitrated compounds such as explosives have high electron affinities and are generally best observed as negative ions. Thus, the nitro derivatives of DPA are expected to produce anions. Positive ions can also be seen from atmospheric pressure chemical ionization with nitrotoluenes [19], indicating that the nitro derivatives of DPA could also produce positive ions. Zeichner and Eldar [20] investigated the use of IMS for gunpowder residues analysis but only NG and DNT were looked for, not the stabilizers. The goal of this study was to investigate the usefulness of IMS for gunpowder stabilizers detection, which, to our knowledge, was never reported so far. This paper presents the study of positive and negative ions produced by EC, DPA and its major nitroso and nitro derivatives. In the negative ion mode, the influence of the addition of a chlorinated reactant was also investigated. Besides, some practical applications of this technique to real-world samples were also tested.

2. Experimental 2.1. Ion mobility spectrometer The ion mobility spectrometer used is a GC-IONSCAN1 M400B (Smiths Detection, USA), operated in the IMS mode. Samples can be analyzed either in the positive ion mode or in the negative ion mode. Plasmagrams were recorded using the IONSCAN System Management software, operated on a personal computer. A schematic representation of the ion mobility spectrometer is adapted from ref. [21] in Fig. 2. The sample is deposited on a sample filter and placed on the desorber heater. The sample molecules are then vapourized and carried through the heated transfer line to the ionization chamber in a flow of dry air carrier gas, possibly containing an additional reactant. The vapours are ionized by high energy electrons produced by a 63Ni beta emitter. Both positive and negative ions are formed. Depending on the mode being employed, positive or negative ions are gated (every 20 or 22 ms, with a pulse width of 0.2 ms) into the drift tube, through which they move to a collector electrode under the influence of an electric field and against a counterflow of dry air drift gas containing a calibrant. The operating conditions used are detailed in Table 1. 2.2. Chemicals Explosives, stabilizers and nitro derivatives of diphenylamine will be referred to with an abbreviation rather than by name. In Table 2, the abbreviations most often used are

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Table 1 IMS operating conditions

Table 2 Abbreviations for the organic compounds used in this study

Ion mode

Parameter

Setting

Abbreviation

Compound name

Positive

Drift tube temperature (8C) Inlet temperature (8C) Desorber temperature (8C) Calibrant temperature (8C) Drift flow (mL/min) Sample flow (mL/min) Analysis time (s) Pulse duration (ms) Scan cycle time (ms) Scan number per segment Segment number per analysis

237 285 285 67 300 200 8 0.2 20 20 20

NG 2,4-DNT 2,6-DNT TNT EC

Drift tube temperature (8C) Inlet temperature (8C) Desorber temperature (8C) Calibrant temperature (8C) Drift flow (mL/min) Sample flow (mL/min) Analysis time (s) Pulse duration (ms) Scan cycle time (ms) Scan number per segment Segment number per analysis

105 240 225 63 351 300 6.6 0.2 22 20 15

Nitroglycerine 2,4-Dinitrotoluene 2,6-Dinitrotoluene 2,4,6-Trinitrotoluene Ethyl centralite (N,N’-diethyl-N,N’-diphenylurea) Diphenylamine N-Nitrosodiphenylamine 2-Nitrodiphenylamine 4-Nitrodiphenylamine 4-Nitrosodiphenylamine 2,4-Dinitrodiphenylamine 2,40 -Dinitrodiphenylamine N-Nitroso-2-nitrodiphenylamine

Negative

In the positive mode, typical operating conditions for drug detection are used. In the negative mode, typical operating conditions for explosive detection are used.

identified by IUPAC name and the structures of the molecules are represented in Figs. 1 and 3. Solvents used were HPLC grade ethanol, acetone and methylene chloride. One microgram per litre standard solutions of all compounds were prepared in ethanol. Solutions of both the individual compounds and a mixture of all compounds were prepared. All

DPA N-NODPA 2-NDPA 4-NDPA 4-NODPA 24-NDPA 240 -NDPA N-NO-2-NDPA

solutions were kept in the dark, in a refrigerator, to prevent decomposition of the nitro and nitroso derivatives [6]. The highly nitrated DPA derivatives with two or more nitro groups appear late in the decomposition process of NC and are generally of secondary interest. However, to test the applicability of the method to identify highly nitrated derivatives, we also included some dinitrated derivatives in this study. A few other compounds (NG, 2,4-DNT, 2,6-DNT and TNT, represented in Fig. 3), known to occur in combinations in regularly encountered gunpowders, were selected and analyzed as well, so as to ensure that they would not interfere with the stabilizers analysis. 2.3. Gunpowder sample preparation The method was tested with selected smokeless gunpowders, to investigate the possibility of detecting EC, DPA and its

Fig. 3. Structures of the other organic compounds analyzed. (1) TNT, (2) 2,4-DNT, (3) 2,6-DNT, (4) NG and (5) EC.


nitrated derivatives in real samples, where other substances might interfere. Five different balls gunpowders were analyzed. The compositions of the different gunpowders were unknown to us. The gunpowder is extracted from the cartridge, weighted and dissolved in 10 mL acetone in order to break the nitrocellulose pellets. Acetone is then evaporated to dryness and 5 mL methylene chloride are added. The residue is filtered to separate NC from the other organic components. The residue is again washed twice with 5 mL methylene chloride. Methylene chloride is a very good solvent for stabilizers and allows to separate them from NC and from inorganic salts also present in gunpowder compositions. However, chloride ions participate in the ionization chemistry in negative mode. As we wish to investigate the negative ionization chemistry with and without the chloride ion, methylene chloride must be eliminated. Thus, methylene chloride is evaporated to dryness and the residue is dissolved again in 5 mL ethanol. 2.4. Analysis procedure The sample solution was deposited in varied amounts onto a sample filter using a microlitre syringe. Solvent can be considered as a contaminant in IMS as competitive ion/molecule reactions occur that mask the response of the analyte [22]. Besides, when the solvent is present in the reaction chamber, aggregates of analyte and solvent can be formed and lead to different types of ions. Thus, throughout the experiments, a drying time of 30 s was applied, to let the solvent evaporate to dryness. All solutes were analyzed separately to determine the reduced mobility constants of their product ions formed in each operated condition, and then the mixture of all solutes was injected, to check the ability of the IMS to identify all species in the presence of possible interferents. The difficulties of quantification with the IMS are known, therefore, no quantification was attempted in this study. However, the solutes were analyzed in varied amounts to investigate the possible variations in the IMS response when different quantities of analyte are present in the spectrometer. 2.5. Reduced mobility constants and mass assignments The ion mobility constant, K (cm2 V1 s1), much as retention time in chromatography, can be used to identify the analyte from the ion peaks observed. Mobility constants are determined using the relationship: K¼

d tE

(1)

where d is the distance an ion will drift in the measured time t under the electric field E. As the ion moves through the drift gas at atmospheric pressure, under influence of the electric field, it encounters an electrostatic resistance from the drift gas molecules as well as geometric (linked to its size, shape and polarizability) and

95

diffusive forces. The following equation can be used to model these phenomena [23]: 1=2 1=2 3q 2p mþM 1 (2) K¼ 16N kT eff mM V where q is the ion charge, N the gas number density, k Boltzmann constant, Teff the effective temperature of the ion, m the ion mass, M the neutral gas molecule mass and V is the collision cross-section of the ion. The latter is determined by ionic size, shape, symmetry and charge distribution [24]. For the purpose of standardization, as absolute mobility varies as a function of drift gas density, ion mobility reduced to standard temperature and pressure, K0, is preferably reported: 273 P K0 ¼ K (3) T 101; 325 where T is the temperature (in K) and P is the pressure (in kPa). In practice, a reference ion (the ‘‘calibrant’’) is used to determine K0. The calibrant mobility is used to correct daily K0 values. Using reduced mobilities from the litterature [21], a graph of 1/K0 versus ion mass was constructed, from which approximate molecular weights of the ions observed could be determined. Then proposals were made for the identities of the ions. Mass assignments based upon mobility are in general only accurate to 20% [25]. The exact nature of the species formed in the IMS can only be decisively determined using IMS–MS combination. Thus, the identities suggested for the varied ions observed should be regarded as speculative. 3. Results and discussion 3.1. Positive ion mode In the positive mode of the IONSCAN, the drift gas contains trace amounts of nicotinamide (NTA) used as both calibrant and reactant. The analyte molecule gets ionized, according to the following proton transfer reaction: ½NTAHþ þ M ! NTA þ MHþ

(4)

This reaction only proceeds if the proton affinity of the sample molecule is greater than that of NTA [22]. Ion lifetimes must also be considered as variables for optimum response or resolution [16]. Instances where response is not observed for an analyte can be attributed to ion instability or low proton affinity. The reduced mobility constants (K0) of the dominant peaks for each compound were calculated and are listed in Table 3. EC and DPA were both seen to produce one well-resolved ion peak. The ion produced by EC is apparently thermally and chemically very stable as the amplitude of the peak is largely higher than that of DPA analyzed in identical quantities. Fig. 4a and b show their product ion spectra, also called plasmagrams. The identity of the response ions has not been determined by coupling the ion mobility spectrometer with a mass spectrometer, but the reduced mobility is consistent with that of the

96


Table 3 Reduced mobilities (K0) and proposed identities of the observed ions obtained when stabilizers are analyzed in positive ion mode Compound

MW

K0 (cm2 V1 s1)

Estimated MW

Proposed identity +

Proposed MW

EC DPA

268 169

1.24 1.61

267 152

ECH DPAH+

269 170

N-NODPA

198

1.08 1.03

345 368

(M–NO)(M–NO)H+ (M–NO)(M–NO)NO+

337 366

2-NDPA 4-NDPA 4-NODPA

214 214 198

1.46 – 1.47

190

MH+

215

188

MH+

199 +

N-NO-2-NDPA

243

1.47 1.52

189 175

(M–NO)H (M–NO2)H+

214 198

24-NDPA 240 -NDPA

259 259

– 1.47

189

(M–NO2)H+

214

MW is the mass of the neutral molecule Estimated MW is the molecular weight estimated from the reduced mobility. Proposed MW is the molecular weight of the proposed identity.

Fig. 4. Positive ion spectra of: (a) EC, (b) DPA and (c) N-NODPA.

C. West et al. / Forensic Science International 166 (2007) 91–101 Table 4 Reduced mobilities (K0) of the observed ions obtained when stabilizers are analyzed in negative ion mode, with hexachloroethane Compound

MW

K0 (cm2 V1 s1)

Estimated MW

EC DPA N-NODPA 2-NDPA 4-NDPA 4-NODPA

268 169 198 214 214 198

– – – – 1.24 1.27

315 303

N-NO-2-NDPA

243

1.24 1.17

317 353

24-NDPA

259

1.25

311

240 -NDPA

259

1.18 1.11

351 390

MW is the mass of the neutral molecule Estimated MW is the molecular weight estimated from the reduced mobility.

nondissociated product ion, ionized through a proton attachment process. Indeed, judging by the calculated mass of the ions produced by EC and DPA, it is reasonable to assume that these are the molecular ions. Extensive quantitative investigations of response factors have not yet been attempted, although the approximate limit of detection for EC was determined to be in the range of 0.5–1 ng; for DPA, it was approximately 2 ng. The low mobility of the two ions produced by N-NODPA (Fig. 4c) suggests the formation of dimers. Actually, N-NODPA is known to denitrosate during thermospray mass spectrometry at 250 8C [4]. A DPA radical is formed as a result. Then two DPA radicals can combine to form tetraphenylhydrazine (MW 337). This dimer (presenting a reduced mobility K0 = 1.075 cm2 V1 s1), can only appear when large amounts of N-NODPA are introduced in the IMS. The second ion (with a reduced mobility K0 = 1.033 cm2 V1 s1) observed may be a dimer-adduct of some sort, possibly a tetraphenylhydrazine-nitroso adduct. The other nitro and nitroso derivatives of DPA apparently do not face such a reaction, as no other heavy ion is observed. Therefore, the presence of the two dimer peaks is diagnostic of N-NODPA. The identity of the cations produced by the nitro and nitroso derivatives of DPA is not clear. Two types of ions seem to be formed: one with a mobility constant close to 1.47 cm2 V1 s1, and the other with a mobility constant of 1.52 cm2 V1 s1.

97

According to the mass calculations, degraded product ions can be suggested for some of them. The gas phase basicity is related to the proton affinity and to the three-dimensional structure of the analyte [26]. Therefore, the isomers of a compound can form different types of ions because of their geometrical structure, or their internal charge distribution, or both. Furthermore, these characteristics can also induce different mobilities for isomeric species. As a result, 4-NDPA and 2,4-NDPA do not produce any visible cation, although their isomeric forms 2-NDPA and 2,40 -NDPA do. 3.2. Negative mode 3.2.1. With chlorinated reactant An important variation of IMS ionization, that can be used to enhance the sensitivity and selectivity of the technique for particular classes of compounds, or to simplify the response for certain analytes, involves the addition of reactants to the drift gas. In the negative ion mode, the internal calibrant in IONSCAN is 4nitrobenzonitrile and the reactant is hexachloroethane. The hexachloroethane reactant yields alternate reactant ions such as Cl, NO3 or NO2. Consequently, ions formed with explosives in IMS occur through APCI reactions using Cl, NO3 or NO2 [19]. NO3 or NO2 are generated from the nitrated solute itself and are consumed in the ion source through association with other solute molecules. These processes can be described by Eqs. (5)–(7): e þ M ! NOx þ ðMNOx Þ

(5)

NOx þ M ! MNOx

(6)

Cl þ M ! MCl

(7)

EC and DPA do not produce any visible negative ion. They might not have any proton acidic enough to be subtracted. In most of DPA derivatives, the presence of electro-attracting nitro and nitroso groups on the aromatic ring apparently enhances the acidic character and allows the formation of stable anions (see Table 4). An example is given with the spectrum produced by 2,4-NDPA (Fig. 5). Again the isomeric forms show different behaviours: 2-NDPA does not produce any negative ion, while its isomeric

Fig. 5. Negative ion spectra of 2,4-NDPA, obtained with the chlorinated reactant.

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form 4-NDPA does; N-NODPA does not produce any negative ion, while its isomeric form 4-NODPA does; the di-nitro isomers 2,4-NDPA and 2,40 -NDPA produce peaks with different mobilities. Often, the gas phase chemistry of nitrotoluenes can be described simply as the formation of M or (M–H), depending upon the availability of a proton abstracting reagent ion (such as Cl) and the acidity of protons. Thus, nitrated derivatives of DPA were expected to produce molecular negative ions. However, the calculated molecular weights of the ionic species formed are higher than what would be expected on the basis of molecular ion structure. Therefore, the formation of adducts with chlorine – originating from the hexachloroethane reactant – and nitro groups is probable.

Table 5 Reduced mobilities (K0) of the observed ions obtained when stabilizers are analyzed in negative ion mode, without hexachloroethane Compound

MW

K0 (cm2 V1 s1)

Estimated MW

EC DPA N-NODPA 2-NDPA

268 169 198 214

– – – 1.34

271

4-NDPA

214

1.34 1.24 1.17 1.13 1.09

270 317 352 377 401

47 35 25 24

1.37 1.27 1.20 1.15 1.12

257 302 338 364 386

45 36 26 22

1.34 1.25 1.17 1.13 1.09

270 315 352 377 401

45 37 25 24

1.37 1.27 1.24 1.20 1.15 1.11

257 303 315 338 364 388

46 12 23 26 24

1.34 1.24 1.18 1.11

270 317 349 389

47 32 40

4-NODPA

198

3.3. Without chlorinated reactant From our own experience of explosive analysis in IMS, the chlorine reactant ion chemistry is not always able to resolve peak overlap of analytes. This point was also observed by Daum et al. [27], who showed that the resolution of analytes can sometimes be achieved using only purified air for the formation of reactant ions. In particular, we observed a lower detection limit for dinitrotoluenes, possibly due to a higher stability of the ions formed in the absence of the chlorinated reactant. Furthermore, the different isomers of DNT could be discriminated as their mobilities were slightly different, while they are all identical when hexachloroethane is used. Thus, for particular compounds, both selectivity and sensitivity could be enhanced by this mean. For this reason, we investigated the ionization occuring when suppressing the hexachloroethane reactant in negative mode. The results are presented in Table 5. As was already observed when hexachloroethane was used as a reactant, EC, DPA and N-NODPA do not produce any visible negative ion. Again, the isomeric species show different behaviours: 2-NDPA produces a unique ion (see Fig. 6a) while 4-NDPA produces five ions, one of them being very close to the 2-NDPA ion; 4-NODPA produces five ions (see Fig. 6b) while N-NODPA produces none; 2,4-NDPA produces six ions while 2,40 -NDPA produces three ions. The peaks produced by N-NO-2-NDPA, 4-NODPA, 4NDPA, 2,4-NDPA and 2,40 -NDPA seem to be produced by the formation of similar adducts, as the difference in the calculated mass between consecutive ions (DMW in Table 5) are nearly identical. Therefore, the clustered groups may be of the same nature, but the identity of the respective ions remains in question. It has to be emphasized that, in this particular case, coupling the ion mobility spectrometer to a mass spectrometer in an attempt to identify the product ions might be of no help as the adduct ions might not survive the transition between the high ambient pressure and the very low pressure necessary for the MS analysis: weakly bound cluster ions might be collisionally decomposed in the interface region. The IONSCAN uses purified ambient air, which may contain a variety of chemicals, for both drift gas and carrier

N-NO-2-NDPA

24-NDPA

240 -NDPA

243

259

259

DMW

MW is the mass of the neutral molecule estimated MW is the molecular weight estimated from the reduced mobility. DMW is the difference in the estimated molecular weight of two consecutive ion peaks.

gas. Indeed, room air commonly produces three to five reactant ions [28]. Many ion/molecule reactions will occur within the source residence time. The reactant ions in negative polarity are thermalized electrons in nitrogen and are hydrated O2 and CO2 [19]. But, if the solvent is not well evaporated before the analysis, clusters formed with solvent molecules (ethanol, in this case) must also be considered. When high-temperature operation with counter current drift-gas flow is employed, humidity effects from air samples introduced into the IMS are normally not observed [29]. Thus, in the present operating conditions, water molecules aggregates should not be observed. Increasing the temperature in the drift tube might eliminate some of the clusters formed, thus favouring a simpler ion mobility spectrum, but the temperature conditions are supposedly optimized for explosive detection, therefore no attempt was made at varying the temperature. Whatever the reason for these multiple peaks, and although some peaks for all these species are not clearly separated due to similar drift times, the IMS could still discriminate all these analogs when the species were analyzed in a mixture.


99

Fig. 6. Negative ion spectra of: (a) 2-NDPA and (b) 4-NODPA, obtained without the chlorinated reactant.

3.4. Establishing a detection algorithm The responses observed for all the substances evaluated in this paper in all modes of operation tested are reported in Table 6. It can be observed that any substance tested can be analyzed with IMS, be it in the positive or the negative ion mode, with or without the chlorinated reactant. It is also of value that 2-NDPA and 4-NDPA, being some of the primary nitro derivatives formed in the gunpowder composition, are detected in two different modes of operation, resulting in a better selectivity after a positive detection in both modes. In any operating mode, when chemical identification of the ions observed was suggested, it cannot be more than speculative. However, the measured values of mobility are characteristic of the sample material and can be used for Table 6 Summary of the response observed when stabilizers are analyzed in positive and negative ion modes, with and without chlorinated reactant Compound

EC DPA N-NODPA 2-NDPA 4-NDPA 4-NODPA N-NO-2-NDPA 24-NDPA 240 -NDPA

Positive mode

Negative mode With Cl

Without Cl

+ + + + +

+ + + + + +

+ + + + + + +

identification in the same manner as retention times are used in chromatography. Nevertheless, a confirmation of the identity of the substance, provided by an orthogonal method, would be required for positive identification. For instance, coupling the IMS after a chromatograph would provide additional information (the chromatographic retention time) about the substance detected by the IMS. By IMS, the production of several peaks for one substance can be helpful. In the presence of an interfering species, unless all peaks were affected, the substance could still be identified. Moreover, multiple peaks reduce the false alarm rate. However, multiple peaks reduce the sensitivity since the species are distributed among more than one ion and quantification is more difficult. In our case, precise qualitative information is preferable to quantitative information. For instance, when analysing the stabilizers mixture in negative mode with the chlorinated reactant, the ion peak produced by 4-NDPA (K0 = 1.24 cm2 V1 s1) could be mistaken for an ion peak produced by N-NO-2-NDPA, having a close mobility (K0 = 1.24 cm2 V1 s1). However, N-NO-2-NDPA also produces a second ion peak with clearly different mobility (K0 = 1.17 cm2 V1 s1). Thus, these two species can be differentiated. Furthermore, the relative intensities of the multiple ion peaks are influenced by concentration effects and by progress through the IONSCAN desorption cycle. Detection algorithms were then developed to take account of the multiple-peak nature of the nitro derivatives of DPA and to accommodate their varying relative intensities and the different patterns occurring when the concentration of the

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Table 7 Summary of the substances identified in gunpowder sample #4 analyzed in positive and negative ions modes, with and without the chlorinated reactant Compound

EC DPA N-NODPA 2-NDPA 4-NDPA N-NO-2-NDPA NG TNT DNT 2,4-DNT 2,6-DNT

Positive mode

Negative mode With Cl

Without Cl

+ + + + +

+ + +

+ + +

+ +

substance is varied. Thus, the IMS can be used to create a stabilizer profile of the smokeless gunpowder. 3.5. Gunpowder samples Each of the selected powders yielded suitable plasmagrams. No interference was observed. The original premise that IMS could be used to analyze smokeless powder was then confirmed. 4-NODPA was never detected, nor were the di-nitro derivatives 2,4-NDPA and 2,40 -NDPA. This may be because 4-NODPA is a relatively reactive and unstable compound and the gunpowders may be in the early stages of decomposition, where di-nitro derivatives only begin to form. This also confirms that the IMS method and the detection algorithms developed are able to differentiate between the different nitro and nitroso derivatives, although their product ions may sometimes be very close on the ion mobility spectrum. Thus, it is possible to selectively detect a single DPA derivative in a complex mixture. An example is given in Table 7, where the results obtained with sample #4 are presented. It is clear that the use of the positive and negative modes in conjunction is most informative on the composition of the gunpowder. In this case, the analysis performed in negative ion mode without the use of hexachloroethane does not bring any fundamental information, apart from the more precise identification of DNT isomers. In other cases, this point proved to be useful as the detection limit for DNT is lower and DNT could then be detected in the negative ion mode without chlorine reactant, while it was not detected in the negative ion mode when the chlorinated reactant was present. 4. Conclusion The data obtained in the present study show that the method employed could play a valuable role in the definitive analysis of gunpowders in casework samples. Analyses are fast, inexpensive and generate a minimum amount of waste. Moreover, the joint detection of several components of smokeless gunpowder

reduces the possibility of interferences and the identification of gunpowder is therefore more definitive. In comparison to traditionally used TLC method, the technique is two to three orders of magnitude more sensitive. Compared to HPLC with diode-array detection, it is still one order of magnitude more sensitive. Dual-mode detection would allow an operator to screen for EC, DPA and N-NODPA in the positive mode while screening for NG, TNT, DNT and the nitro derivatives of DPA in the negative mode. Other components possibly found in gunpowder compositions could be analyzed by this technique. For instance, the method is surely also suitable for the analysis of methylcentralite, since its structure is so similar to that of EC. Besides, phthalate compounds were reported to produce positive ions [18]. Moreover, Kuja et al. [30] reported the detection of NC in negative ion mode. Therefore, if positive and negative ions were monitored at the same time, as is the case with Ionscan 500DT, a complete analysis of smokeless gunpowder organic compounds could be achieved in one single IMS analysis, in less than 10 s. Nevertheless, for any casework sample, a confirmation provided by an orthogonal method is compulsory. In this respect, the very small amounts of sample required by the IMS analysis are an advantage, as it possibly leaves sample for complementary analyses. References [1] Y. Tong, Z. Wu, C. Yang, J. Yu, X. Zhang, S. Yang, X. Deng, Y. Xu, Y. Wen, Determination of DPA in smokeless gunpowder using a tandem MS method, Analyst 126 (2001) 480–484. [2] J. Yinon, A. Acevedo, T. Chamberlain, S. Brunk, Differentiation between nitroglycerin explosive and nitroglycerin medication using an IMS detector, in: D. Garbutt, P. Pilon, P. Lightfoot (Eds.), Proceedings of the 8th International Symposium on Analysis and Detection of Explosives, 2004, pp. 306–313. [3] O. Drzyzga, Diphenylamine and derivatives in the environment, Chemosphere 53 (2003) 809–818. [4] J.C. Via, L.T. Taylor, Chromatographic analysis of nonpolymeric single base propellant components, J. Chromatogr. Sci. 30 (1992) 106–110. [5] A. Bergens, R. Danielsson, Decomposition of diphenylamine in nitrocellulose based propellants I. Optimization of a numerical model to concentration-time data for diphenylamine and its primary degradation products determined by liquid chromatography with dual amperometric detection, Talanta 42 (1995) 171–183. [6] J.M. Bellerby, M.H. Sammour, Stabilizer reactions in double base rocket propellants, propellants, explosives, Pyrotechnics 16 (1991) 235–239. [7] A. Zeichner, B. Eldar, B. Glattstein, A. Koffman, T. Tamiri, D. Muller, Vacuum collection of gunpowder residues from clothing worn by shooting suspects, and their analysis by GC/TEA, IMS and GC/MS, J. Forensic Sci. 48 (5) (2003) 961–972. [8] O. Cascio, M. Trettene, F. Botolotti, G. Milana, F. Tagliaro, Analysis of organic components of smokeless gunpowders: HPLC vs. Micellar electrokinetic capillary chromatography, Electrophoresis 25 (2004) 1543–1547. [9] A. Bergens, Decomposition of diphenylamine in nitrocellulose based propellants II. Application of a numerical model to concentration–time data determined by liquid chromatography and dual-wavelength detection, Talanta 42 (1995) 185–196. [10] J.B.F. Lloyd, Liquid chromatography of firearms propellant traces, J. Energetic Mater. 4 (1986) 239–271.

C. West et al. / Forensic Science International 166 (2007) 91–101 [11] H. Meng, B. Caddy, Detection of N,N0 -diphenyl-N,N0 -diethylurea (ethylcentralite) in gunshot residues using high-performance liquid chromatography with fluorescence detection, Analyst 120 (1995) 1759–1762. [12] Z. Wu, Y. Tong, J. Yu, X. Zhang, C. Pan, X. Deng, Y. Xu, Y. Wen, Detection of N,N0 -diphenyl-N,N0 -dimethylurea (methyl centralite) in gunshot residues using MS–MS method, Analyst 124 (1999) 1563–1567. [13] M. Ashraf-Khorassani, L.T. Taylor, Qualitative supercritical fluid chromatography/Fourier transform infrared spectroscopy study of methylene chloride ans supercritical carbon dioxide extracts of double-base propellant, Anal. Chem. 61 (1989) 145–148. [14] Y. Tong, Z. Wu, C. Yang, J. Yu, X. Zhang, S. Yang, X. Deng, Y. Xu, Y. Wen, Determination of diphenylamine in smokeless gunpowder using a tandem MS method, Analyst 126 (2001) 480–484. [15] G.A. Eiceman, Z. Karpas, Ion Mobility Spectrometry, CRC Press, Boca Raton, FL, 1994. [16] G.A. Eiceman, Ion mobility spectrometry as a fast monitor of chemical composition, Trends Anal. Chem. 21 (2002) 259–275. [17] Z. Karpas, Ion mobility spectrometry of aliphatic and aromatic amines, Anal. Chem. 61 (1989) 684–689. [18] G. Simpson, M. Klasmeier, H. Hill, D. Atkinson, G. Radolovich, V. LopezAvila, T.L. Jones, Evaluation of gas chromatography coupled with ion mobility spectrometry for monitoring vinyl chloride and other chlorinated and aromatic compounds in air samples, J. High Resolut. Chromatogr. 19 (1996) 301–312. [19] R.D. Ewing, D.A. Atkinson, G.A. Eiceman, G.J. Ewing, A critical review of ion mobility spectrometry for the detection of explosives and explosive related compounds, Talanta 54 (2001) 515–529. [20] A. Zeichner, B. Eldar, A new method for extraction and analysis of gunpowder residues on double-side adhesive coated stubs, J. Forensic Sci. 49 (2004).

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[21] Anonymous, GC-IONSCAN1 Model 400B Operator’s Manual, Smiths Detection, USA. [22] T. Keller, A. Miki, P. Regenscheit, R. Dirnhofer, A. Schneider, H. Tsuchihashi, Detection of designer drugs in human hair by ion mobility spectrometry, Forensic Sci. Int. 94 (1998) 55–63. [23] H.E. Revercomb, E.A. Mason, Theory of plasma chromatography/gaseous electrophoresis—a review, Anal. Chem. 47 (1975) 970–983. [24] N. Agbonkonkon, H.D. Tolley, M.C. Asplund, E.D. Lee, M.L. Lee, Prediction of gas-phase reduced ion mobility constants (Ko), Anal. Chem. 76 (2004) 5223–5229. [25] G.W. Griffin, I. Dzidic, D.I. Carroll, R.N. Stillwell, E.C. Horning, Ion mass assignments based on mobility measurements, Anal. Chem. 45 (1973) 1204–1209. [26] Y. Guo, M.Q. Lu, Y.T. Long, Ion mobility spectra of selected amines and their application in field testing with the use of a portable IMS device, Field Anal. Chem. Technol. 1 (4) (1997) 195–211. [27] K.A. Daum, D.A. Atkinson, R.G. Ewing, W.B. Knighton, E.P. Grimsrud, Resolving interferences in negative mode ion mobility spectrometry using selective reactant ion chemistry, Talanta 54 (2001) 299–306. [28] P. Rodacy, P. Leslie, S. Klassen, R. Silva, Ion mobility spectroscopic techniques for the detection and identification of explosives, in: C.R. Midkiff (Ed.), Proceedings of the 5th International Symposium on Analysis and Detection of Explosives, 1997. [29] H.H. Hill, G. Simpson, Capabilities and limitations of ion mobility spectrometry for field screening applications, Field Anal. Chem. Technol. 1 (3) (1997) 119–134. [30] F. Kuja, A. Grigoriev, R. Debono, S. Nacson, Ion mobility spectrometry in the detection of improvised explosives, in: A. Cumming (Ed.), Proceedings of the 7th International Symposium on Analysis and Detection of Explosives, 2001, pp. 179–184.


A study of the use of Ephedra in the manufacture of methamphetamine W.D. Barker a,*, U. Antia b a

Institute of Environmental Science and Research Ltd (ESR), Mt Albert Research Centre, Hampstead Road, Private Bag 92021, Auckland, New Zealand b University of Auckland, Department of Chemistry, Auckland, New Zealand Received 20 February 2006; received in revised form 2 April 2006; accepted 9 April 2006 Available online 16 May 2006

Abstract The Ephedra plant has been identified as an excellent source of ephedrine and pseudoephedrine, both of which can be chemically reduced to form the widely abused illicit drug methamphetamine. Ephedra contains several additional alkaloids that undergo analogous reductions to form amphetamine and N,N-dimethylamphetamine (also drugs of abuse). The main alkaloids obtained from the Ephedra plant have been reduced using four common methods used by the clandestine operator. The intermediates and byproducts of these reductions have been identified and/or tentatively assigned and the mechanism of formation discussed. # 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Ephedra; Methamphetamine; Amphetamine; Dimethylamphetamine; Reduction; Intermediate; Byproduct

A frequently encountered method for the clandestine manufacture of methamphetamine involves the conversion of pseudoephedrine and/or ephedrine to methamphetamine by reduction [1]. Pseudoephedrine and ephedrine are commonly obtained from pharmaceutical preparations, which are often available from drug stores or pharmacies (depending on local legislation). An alternative source of ephedrine and pseudoephedrine is the naturally occurring plant Ephedra. Ephedra is a primitive stalky plant that contains numerous alkaloids including ephedrine and pseudoephedrine. The ground up plant material (also referred to as Ma Huang) is frequently seen in tablet, capsule or powdered form. Ma Huang is a Chinese herbal remedy used to relieve respiratory related ailments such as bronchitis and asthma [2]. There have been more than 30 different species of Ephedra found, mainly in subtropical and temperate regions of Europe, Asia and America. However, only a few of these species contain ephedrine related alkaloids at any significant level [3]. The main alkaloids present in Ephedra are the physiologically active diastereomeric pairs ()-ephedrine and (+)-pseudoephedrine; ()-methylephedrine and (+)-methylpseudoephedrine;

* Corresponding author. Tel.: +64 98153949. E-mail address: [email protected] (W.D. Barker). 0379-0738/$ – see front matter # 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.forsciint.2006.04.005

()-norephedrine and (+)-norpseudoephedrine (Fig. 1). The enantiomers of the six compounds in Fig. 1 are not physiologically active and have not been observed in nature. Previous quantitative studies show that alkaloid levels vary widely inter and intra species and in general ephedrine and pseudoephedrine are more abundant than norephedrine and norpseudoephedrine which are, in turn, more abundant than methylephedrine and methylpseudoephedrine [2]. Locally sourced Ephedra americana and Ephedra campylpoda were found to contain approximately 1% total alkaloid (dry weight).1 Fig. 1 clearly illustrates that the alkaloids differ only by the alkylation of the amine and this is carried through in the main reduction product of each pair of diastereoisomers. As expected the tertiary amine pair ()-methylephedrine and (+)-methylpseudoephedrine yield (+)-N,N-dimethylamphetamine, the secondary amine pair ()-ephedrine and (+)-pseudoephedrine yield (+)-methamphetamine and the primary amine pair ()norephedrine and (+)-norpseudoephedrine yield (+)-amphetamine [4]. From a forensic chemist’s perspective it is the presence of each of these compounds in an illicit sample that can provide information on the original source of the sample. For example,

1 The extraction of these alkaloids can be variable depending on technique and solvents used (U. Antia, unpublished results).

W.D. Barker, U. Antia / Forensic Science International 166 (2007) 102–109

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Fig. 1. The six physiologically active ephedrine related alkaloids found in Ephedra and their three reduction products.

if a methamphetamine product contains a small amount of amphetamine and N,N-dimethylamphetamine then Ephedra is the likely precursor in the manufacturing process [5]. A further tool available to the forensic chemist is the identification of other byproducts, reaction intermediates and impurities in samples associated with the clandestine methamphetamine manufacturing process. The detection of these additional compounds within a sample often provides information on the synthetic route used to produce a particular product. For example, cis- and trans-1,2-dimethyl-3-phenylaziridine, 1-phenyl-2-propanone, 1,3-dimethyl-2-phenylnaphthalene and 1-benzyl-3-methylnaphthalene are route specific intermediates and byproducts of the manufacture of methamphetamine using any of the many variations of the hydriodic acid reduction of pseudoephedrine/ephedrine (Fig. 2) [6–8]. This article expands upon previous work by investigating several frequently observed methods of clandestine methamphetamine manufacture using each of the six main Ephedra alkaloids as a precursor. Intermediates and byproducts have been identified and evaluated providing the forensic chemist with additional information for the investigation of clandestinely produced drugs. 1. Materials and instrumentation Anhydrous ammonia gas was purchased from BOC Gases. Pseudoephedrine, norephedrine and norpseudoephedrine were purchased from Acros Organics. Lithium metal was obtained

from lithium AA batteries (Energizer). Methylephedrine and methylpseudoephedrine were manufactured in the laboratory from ephedrine and pseudoephedrine using previously published syntheses and characterized prior to use [9]. Ephedrine hydrochloride was a seized sample and was characterized prior to use using authenticated standards. Thionyl chloride was purchased from Scharlau Chemie. Palladium chloride was also seized but originated from Kee Shing Industrial Products. Barium sulfate was purchased from Panreac Quimica SA. All other chemicals and solvents were purchased from BDH Laboratory Supplies. Gas chromatography–mass spectrometry (GCMS) analysis was conducted using an Agilent 6890N Network Gas Chromatograph with a 5973N inert Mass Selective Detector. A 25 m BPX5 220 mm i.d. column with a 0.25 mm film thickness was used with helium carrier gas. After 2 min at 70 8C, the temperature was ramped to 300 8C at 30 8C/min. The samples were prepared by extraction into chloroform. Nuclear magnetic resonance (NMR) was conducted using a Bruker Biospin AVANCE DRX 400 spectrometer at 400.17 MHz for proton NMR and 100.61 MHz for carbon NMR. The samples were dissolved in deuterated chloroform for analysis. The following reductions were carried out using variations of previously reported methods: red phosphorus and iodine reduction [6,7,8], hypophosphorous acid and iodine reduction [10], dissolving metal reduction [11–13] and metal catalysed reduction [14,15]. Specific details of the reduction reactions and analytical data are available from the author.

Fig. 2. Route specific intermediates and byproducts of the hydriodic acid reduction of pseudoephedrine/ephedrine [6–8].

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2. Results and discussion The four frequently encountered reduction reactions investigated were two variations of the hydriodic acid reduction, a dissolving metal reduction and a metal catalysed hydrogenation (via a chloro-intermediate). All four reductions were carried out on each of the six main Ephedra alkaloids and the reaction progress monitored by GCMS. Acidic and basic extracts of the reaction mixtures were taken at time intervals to evaluate the maximum number of byproducts and intermediates.

2.1. Hydriodic acid reduction Hydriodic acid can be used to directly reduce benzyl alcohols under reflux conditions, however, during the clandestine manufacture of methamphetamine it is more common to proceed via the in situ generation of the reactive ‘‘HI’’ species. The reduction is believed to progress via an iodo intermediate of the alkaloid by displacement of the hydroxyl group with the iodo anion [1]. While the iodoephedrine (or equivalent) is never isolated within the reaction mixture, previous mechanistic studies add significant weight to this hypothesis [6–8]. Two frequently encountered methods for ‘‘HI’’ production involve mixing iodine with red phosphorus in the presence of water or mixing hypophosphorous acid with iodine. Both of these methods were used during this investigation. The only difference in results was the time scale of intermediate, byproduct and product formation. The hypophosphorous acid/iodine reduction was significantly faster than the red phosphorus/iodine reduction. As discussed previously, the reduction of ephedrine by hydriodic acid generates a number of intermediates and byproducts (Fig. 2), which can be observed forming during a reaction. Previous studies show that as the reduction progresses, ephedrine is consumed while the aziridines (cis- and trans-1,2dimethyl-3-phenylaziridine) evolve. Over time a new species 1phenyl-2-propanone (P-2-P) forms, as does methamphetamine. Towards the end of the reaction time scale, the aziridines disappear and the naphthalenes (1,3-dimethyl-2-phenylnaphthalene and 1-benzyl-3-methylnaphthalene) begin to form [6–8]. It is well accepted that the aziridine intermediates2 are formed by elimination of iodide from the iodo intermediate. During the progress of the reaction, the aziridines are consumed as they are either reduced to methamphetamine or hydrolysed to form P-2-P. Over time, P-2-P dimerises via an acid catalysed intermolecular condensation to give the naphthalenes. Pseudoephedrine undergoes similar reduction resulting in the same byproducts and intermediates [6–8].

Fig. 3. Reaction progress of the red phosphorus/iodine reduction of norephedrine (base-ether extraction of an aliquot of reaction mixture at t = 30 min, analysed by GCMS).

Norephedrine reduced to amphetamine under the same conditions. The reaction progressed in a similar manner and gave rise to the expected intermediates (Fig. 3). In this instance, the aziridines observed were, as expected, cis- and trans-3-phenyl-2-methylaziridine. Small amounts of P2-P were observed in low levels in an acid extraction of the reaction mixture, however, during chromatography P-2-P coelutes with amphetamine and is therefore not readily identified. As the reaction progressed, the aziridines were again consumed while the P-2-P condensation products were formed (Fig. 4). An additional peak attributed to the formation of N(b-phenylisopropyl)benzyl-methylketimine was observed at approximately 8.5 min. The ketimine is likely to be a condensation product of P-2-P and the primary amine of amphetamine. Norpseudoephedrine reduced to amphetamine under the same conditions and gave rise to the same byproducts/ intermediates. Methylephedrine reduced to N,N-dimethylamphetamine in a similar manner with the following exception. Basic extracts of the reaction mixture over time were of limited value as they exhibited starting material and product with no additional compounds observed. Acidic extracts (direct ether extract of an aliquot of reaction mixture in water) did not exhibit the aziridine intermediates, however, they did display two new tentatively identified ‘‘intermediates’’: 1-propenylbenzene and 2-propenylbenzene (Fig. 5). The presence of P-2-P in the reaction mixture indicates that aziridines were likely to have formed at some stage, however, they were not observed during the GCMS analysis.

2

While it is not fully agreed that the aziridine species are actually formed during the reduction, they are commonly observed during chromatographic analysis. The actual intermediate responsible for the observed aziridines may be an iminium ion, an enaminium ion, an aziridinium ion or a combination of all three species [6,7,8].

Fig. 4. Reaction progress of the red phosphorus/iodine reduction of norephedrine (base-ether extraction of an aliquot of reaction mixture at t = 90 min, analysed by GCMS).


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Fig. 5. Reaction progress of the red phosphorus/iodine reduction of methylephedrine (acid extraction at t = 15 min, analysed by GCMS).

The predicted aziridine intermediates would be quaternary N-alkylated cis- and trans-1,1,2-trimethyl-3-phenylaziridine. The instability of these charged intermediates during chromatographic conditions may lead to the formation of the benzylpropenes by elimination. The fact that during the progress of the reaction, the benzylpropenes disappear adds weight to this hypothesis. If the benzylpropenes were in fact formed during the reaction, as relatively unreactive byproducts (rather than eliminated intermediates), they should remain unchanged in the final reaction mixture. Methylpseudoephedrine also reduced to N,N-dimethylamphetamine under the same conditions and gave rise to the same byproducts/intermediates. 2.2. Dissolving metal reduction The dissolving metal reduction reaction was developed during the 1940s as a method for synthesising cyclohexadienes from arenes [16]. More recently, the utility of lithium/ammonia in the selective reduction of benzyl alcohols has been recognised [17]. This has subsequently led to the technique being used extensively in the clandestine manufacture of methamphetamine [11–13]. The reduction of the Ephedra alkaloids to their related amphetamines has been previously studied and is believed to occur via an electron-mediated process leading to the heterolytic cleavage of the hydroxyl group [11]. A limitation of this reaction is the over-reduction of the amphetamine product when an excess of the alkali metal is present in the reaction mixture. For example samples of methamphetamine produced in a clandestine environment often contain a byproduct, which has recently been identified as 1-(10 ,40 cyclohexadienyl)-2-methylaminopropane (CMP) [12,18].

Fig. 6. Mass spectra of CMP (byproduct formed during the manufacture of methamphetamine by reduction using the lithium ammonia method).

Fig. 7. Mass spectra of byproducts of norephedrine/norpseudoephedrine reduction (top) and methylephedrine/methylpseudoephedrine reduction (bottom) and tentatively assigned structures.

The protons required for the reduction of the hydroxyl group and the partial reduction of the aromatic ring arise because of damp or impure solvents or even water absorbed into the reaction from the atmosphere. CMP is another route specific byproduct and is indicative of a methamphetamine sample being synthesised by this method. Reproduction of the reduction of pseudoephedrine and ephedrine using a previously published method resulted in methamphetamine and a small amount of the CMP byproduct. The mass spectra of CMP, observed in both reduction reactions, was consistent with the literature (Fig. 6) [12,18]. Norephedrine and norpseudoephedrine were reduced to amphetamine using the same conditions, while methylephedrine and methylpseudoephedrine were reduced to N,Ndimethylamphetamine. In each reaction, a minor byproduct was observed. The byproducts were tentatively identified by comparison to the previously characterized reduction product CMP (Fig. 7).3 The parent ion of the amphetamine byproduct {m/z 136 (M 1)}, is 14 mass units (a methylene group) lower than that observed for CMP, thus indicating the CMP analogue 1-(10 ,40 cyclohexadienyl)-aminopropane (CAP). Conversely the parent ion in the N,N-dimethylamphetamine byproduct {m/z 164 (M 1)}, is 14 mass units higher, indicating the CMP analogue 1-(10 ,40 -cyclohexadienyl)-2,2-dimethylaminopropane (CDP). The methylephedrine and methylpseudoephedrine reacted much slower than the less hindered analogues and over the time period of the reaction there was a significant amount of unreacted starting material left. 3 A further minor byproduct previously hypothesised as a CMP ring isomer was also observed at low levels in the reduction of pseudoephedrine and ephedrine to methamphetamine. An analogous byproduct was also seen in the amphetamine and dimethylamphetamine products. However, due to the low relative concentration, the analytical data associated with these compounds is of limited value.

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2.3. Metal catalysed hydrogenation (via chlorointermediate) The benzylic alcohol moiety present in the Ephedra alkaloids cannot be effectively reduced using hydrogenation techniques commonly available to the clandestine chemist. Instead, ephedrine and pseudoephedrine are generally converted to their chloro-derivatives prior to reduction by catalytic hydrogenation. Previous work in the area shows that the chloroderivatives of ephedrine and pseudoephedrine can be synthesised in relatively high yield using a one step process, involving thionyl chloride or phosphorus pentachloride [14,15,19]. There appears to be some disagreement within the literature as to the nature of the chloro-product as Allen and Kiser [14] describe ()-ephedrine leading almost exclusively to (+)-chloropseudoephedrine (99%) via an SN2 process and (+)-pseudoephedrine leading to a 60:40 mixture of (+)-chloropseudoephedrine and ()-chloroephedrine via a combination of SN2 and SNi displacement of the hydroxyl group (quantitated by 1H NMR). In contrast, Soine and co-workers [15] describe chlorination of each alkaloid resulting in a mixture of ()-chloroephedrine. Allen et al. state that while 1H NMR analysis of the chloroalkaloid product demonstrate that the product is pure, analysis by GCMS indicates the presence of cis- and/or trans-1,2dimethyl-3-phenylaziridine. The aziridine compounds are presumably produced by intramolecular ring closure, as the chloro-derivative is introduced into the high temperature conditions of the GCMS. The 1H NMR analysis of the chloro-substituted products derived from ()-ephedrine and (+)-pseudoephedrine were in agreement with the results reported by Allen and Kiser [14]. Our GCMS analysis results of the chloro-alkaloid products were also in agreement with those literature results with the cis- and trans-1,2-dimethyl-3-phenylaziridines observed in

similar ratios (Fig. 8) [14]. In our work, chlorination of ephedrine led to >99% pure chloropseudoephedrine (quantitated by 1H NMR) whereas pseudoephedrine led to an approximately 80:20 mixture of chloro-ephedrines, favouring the SNi product chloropseudoephedrine.4 NMR analysis of the product derived from ()-norephedrine indicated a single compound (>99%), presumably (+)chloronorpseudoephedrine, while the product derived from (+)-norpseudoephedrine appeared to be a mixture of (+)chloronorpseudoephedrine and ()-chloronorephedrine (approximately 80:20 favouring chloronorpseudoephedrine). As close analogues of ()-ephedrine and (+)-pseudoephedrine, it is expected that the chlorine atom substitutions proceed via the same SN2 or combination of SN2 and SNi mechanisms, respectively. The cis- and trans-2-methyl-3-phenylaziridines were not observed during NMR analysis, but were again evident in the GCMS analysis of the chloro-alkaloid products. The aziridines were not well resolved and could not be accurately attributed to the cis- or trans-isomers without further work. In this instance, both chloro-products manifested with a similar cis:trans aziridine ratio (Fig. 9). When ()-methylephedrine was treated with thionyl chloride, it was expected that the single isomer of (+)chloromethylpseudoephedrine would be observed via SN2 substitution, whereas (+)-methylpseudoephedrine should give a mixture of ()-chloromethylephedrine and (+)-chloromethylpseudoephedrine via both SN2 and SNi substitution. It was clear from NMR data obtained, that methylephedrine actually yielded a mixture of chloromethylpseudoephedrine and chloromethylephedrine in an 80:20 mixture. In this instance, it appeared that the SNi substitution was more favourable and some of the product was formed via the aziridine intermediate. As expected methylpseudoephedrine yielded a mixture of chloromethylpseudoephedrine and chloromethylephedrine, although in a 95:5 mixture, thus favouring the SNi mechanism more than the previous analogues. The increased proportion of the stereochemistry retained SNi product in both methylephedrine and methylpseudoephedrine reactions can be attributed to the inductive effect of an additional alkyl group on the nitrogen, stabilizing the quaternary aziridine intermediate. Further evidence that these reactions proceed, in some part, through the SNi pathway is observed in an additional minor byproduct evident in the NMR of each dimethyl-chloroproduct. The new byproduct has been tentatively identified as 1dimethylamino-1-phenyl-2-chloropropane. The aziridine intermediate can undergo favourable C1 attack to furnish the expected SNi product, or C2 attack to yield the less favoured byproduct (Fig. 10). The aziridine intermediates, seen previously, were not observed in the NMR results or during GCMS analysis. Instead the same aryl alkenes that were detected during the ‘‘HI’’

4

Fig. 8. GCMS analysis of chloro-alkaloids derived from (+)-pseudoephedrine (top) and ()-ephedrine (bottom).

While chloropseudoephedrine and chloroephedrine cannot be distinguished by GCMS (same retention time and fragmentation fingerprint), they are easily resolved using NMR spectroscopy.


107

Fig. 9. GCMS analysis of chloro-alkaloids derived from (+)-norpseudoephedrine (top and bottom-left) and ()-norephedrine (bottom-right).

reduction of ()-methylephedrine and (+)-methylpseudoephedrine were observed by GCMS. In these cases the alkenes can again be tentatively attributed to 1-propenylbenzene and 2propenylbenzene. The new byproduct (1-dimethylamino-1phenyl-2-chloropropane) was also observed in the GCMS data, eluting slightly earlier than each of the chloro-products (Fig. 11). The palladium catalysed hydrogenation of the chloroalkaloids all proceeded in high yield, with no discernible byproducts. As expected the chloro-intermediates derived from ()-ephedrine and (+)-pseudoephedrine yielded (+)-methamphetamine, those derived from ()-norephedrine and (+)-

Fig. 10. Hypothesised mechanism of formation of product and by-product by SNi substitution of (+)-methylpseudoephedrine.

norpseudoephedrine yielded (+)-amphetamine and those derived from ()-methylephedrine and (+)-methylpseudoephedrine yielded N,N-dimethylamphetamine. The hydrogenation product of 1-dimethylamino-1-phenyl-2-chloropropane produced during the chlorination of methylephedrine and

Fig. 11. GCMS analysis of chloro-alkaloids derived from ()-methylephedrine (top) and mass spectra of compound tentatively identified as 1-dimethylamino1-phenyl-2-chloropropane (bottom).

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Table 1 Summary of products, byproducts and intermediates produced on reduction of Ephedra derived alkaloids Starting material

Reduction method

Product

Intermediates (Observed by GCMS)

Byproducts (Observed by GCMS)

Ephedrine/ pseudoephedrine

‘‘HI’’

Methamphetamine

cis-/trans-1,2-Dimethyl-3-phenylaziridine

Norephedrine/ norpseudoephedrine

‘‘HI’’

Amphetamine

cis-/trans-3-Phenyl-2-methylaziridine

Methylephedrine/ methylpseudoephedrine Ephedrine/pseudoephedrine

‘‘HI’’

N,N-Dimethylamphetamine Methamphetamine

1-Propenylbenzene 2-propenylbenzene Chloropseudoephedrine chloroephedrine cis-/trans-1,2-dimethyl-3-phenylaziridine Chloronorpseudoephedrine chloronorephedrine cis-/trans-2-methyl-3-phenylaziridine Chloromethylpseudoephedrine chloromethylephedrine 1-dimethylamino-1-phenyl-2chloropropane

1-Phenyl-2-propanone 1,3-dimethyl-2-phenylnaphthalene 1-benzyl-3-methylnaphthalene 1-Phenyl-2-propanone 1,3-dimethyl-2-phenylnaphthalene 1-benzyl-3-methylnaphthalene N-(b-phenylisopropyl)benzylmethylketimine 1-Phenyl-2-propanone

Metal catalysed hydrogenation

Norephedrine/ norpseudoephedrine


Amphetamine

Methylephedrine/ methylpseudoephedrine


N,N-Dimethylamphetamine

Ephedrine/ pseudoephedrine Norephedrine/ norpseudoephedrine Methylephedrine/ methylpseudoephedrine

Dissolving metal (Li/NH3) Dissolving metal (Li/NH3) Dissolving metal (Li/NH3)

Methamphetamine

1-(10 ,40 -Cyclohexadienyl)-2-methylaminopropane (CAP) 1-(10 ,40 -Cyclohexadienyl) aminopropane (CMP) 1-(10 ,40 -Cyclohexadienyl)-2,2-dimethylaminopropane (CDP)

Amphetamine N,N-Dimethylamphetamine

methylpseudoephedrine was not detected, but may co-elute with the strong N,N-dimethylamphetamine peak during GCMS analysis. 3. Summary Previous studies have identified a number of intermediates and byproducts produced during the manufacture of amphetamines. Further compounds, derived from the reduction of Ephedra based alkaloids by several common methods of amphetamine manufacture have been identified or hypothesised and have been described in this article. The products, byproducts and intermediates from the three common reduction methods investigated in this article are summarised in Table 1. 4. Conclusions A number of intermediates and byproducts produced during the reduction of Ephedra alkaloids using several common methods of clandestine methamphetamine manufacture have been identified or hypothesised. The identification of these intermediates and byproducts by GCMS will aid the forensic chemist, when endeavouring to ascertain the source of precursors used in the manufacture of methamphetamine. The information provided here, not only aids the forensic chemist in identifying Ephedra as a precursor for methamphetamine manufacture, but also assists in the elucidation of the synthetic pathway used during the manufacturing process.

References [1] A. Allen, T.S. Cantrell, Synthetic reductions in clandestine amphetamine and methamphetamine laboratories: a review, Forensic Sci. Int. 42 (3) (1989) 183–199. [2] K. Hutchinson, K.M. Andrews, The use and availability of Ephedra products in the United States, Microgram 28 (8) (1995) 256–263. [3] L. Reti, Ephedra Bases, The Alkaloids: Chemistry and Physiology, vol. 3, 1953, pp. 339–362 (Chapter 23). [4] K.M. Andrews, Ephedra’s role as a precursor in the clandestine manufacture of methamphetamine, J. Forensic Sci. 40 (4) (1995) 551–560. [5] L. Pederson, Methamphetamine synthesized from Ephedra extract encountered, J. Clandestine Lab. Investig. Chem. Assoc. 4 (3) (1994) 16–17. [6] H.F. Skinner, Methamphetamine synthesis via hydriodic acid/red phosphorus reduction of ephedrine, Forensic Sci. Int. 48 (2) (1990) 123– 124. [7] T.S. Cantrell, B. John, L. Johnson, A.C. Allen, A study of impurities found in methamphetamine synthesized from ephedrine, Forensic Sci. Int. 39 (1) (1988) 39–53. [8] K.L. Windahl, M.J. McTigue, J.R. Pearson, S.J. Pratt, J.E. Rowe, E.M. Sear, Investigation of the impurities found in methamphetamine synthesised from pseudoephedrine by reduction with hydriodic acid and red phosphorus, Forensic Sci. Int. 76 (1995) 97–114. [9] L. Bernardi, B. Bonini, M. Comes-Franchini, M. Fochi, G. Mazzanti, A. Ricci, G. Varchi, Synthesis and reactivities of enantiomerically pure bhydroxyalkyl and b-aminoalkyl ferrocenyl sulfides, Eur. J. Org. Chem. 26 (2000) 2776–2784. [10] P. Vallely, A single step process for methamphetamine manufacture using hypophosphorus acid, J. Clandestine Lab. Investig. Chem. Assoc. 5 (2) (1995) 14–15. [11] R.A. Ely, D.C. McGrath, Lithium–ammonia reduction of ephedrine to methamphetamine: an unusual clandestine synthesis, J. Forensic Sci. 35 (3) (1990) 720–723.

W.D. Barker, U. Antia / Forensic Science International 166 (2007) 102–109 [12] E.C. Person, J.A. Meyer, J.R. Vyvyan, Structural determination of the principal byproduct of the lithium-ammonia reduction method of methamphetamine manufacture, J. Forensic Sci. 50 (1) (2005) 1–9. [13] T. Dal Cason, A Review of the Birch Reduction Method, Clandestine Laboratory Investigating Chemists Association Monograph, 1998. [14] A.C. Allen, W.O. Kiser, Methamphetamine from ephedrine: 1. Chloroephedrines and aziridines, J. Forensic Sci. 32 (4) (1987) 953– 962. [15] V. Lekskulchai, K. Carter, A. Poklis, W. Soine, GC–MS analysis of methamphetamine impurities: reactivity of (+)- or ()-chloroephedrine

[16] [17]

[18]

[19]

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and cis- or trans-1,2-dimethyl-3-phenylaziridine, J. Anal. Toxicol. 24 (2000) 602–605. A.J. Birch, Reduction by dissolving metals. Part 1, J. Chem. Soc. (1944) 430–436. S.S. Hall, S.D. Lipsky, G.H. Small, Selective lithium–ammonia reduction of aromatic ketones and benzyl alcohols: mechanistic implications, Tetrahedron Lett. 12 (1971) 1853–1854. G. Zvilichovsky, I. Gbara-Haj-Yahia, Birch reduction of ()-ephedrine. Formation of a new versatile intermediate for organic synthesis, J. Org. Chem. 69 (16) (2004) 5490–5493. H. Emde, Uber Diastereomerie III. Chlor- und brom-ephedrine, Helvetica Chemica Acta 12 (1929) 384–399.


Examination of a long-term clozapine administration by high resolution segmental hair analysis Detlef Thieme a,b,*, Hans Sachs a,b a

Institute of Forensic Medicine, Frauenlobstr. 7a, 80337 Munich, Germany b Forensic Toxicological Centre, Bayerstr. 53, 80335 Munich, Germany

Received 3 December 2005; received in revised form 17 April 2006; accepted 21 April 2006 Available online 12 June 2006

Abstract The long-term administration of clozapine could be verified by fine segmentation and analysis of single hairs of one person to examine the history of a multiple poisoning case. Segments of 1–2.5 mm length were extracted by ultrasonification in 30 ml of the mobile phase (mixture of methanol + water, 50 + 50). By application of isocratic liquid chromatography and using narrow bore columns (Synergy Polar-RP, Phenomenex), an acceleration and miniaturization of the HPLC–MS–MS assay could be achieved. Total amounts of clozapine down to 30 fg (on column) and its desmethyl metabolite could be analysed in multiple reaction monitoring mode. According to typical sample amounts of 16 mg, relevant hair concentrations higher than 1 pg/mg were detected. Significant and reproducible concentration profiles along the hair fibres revealed characteristic administration cycles. The administration time course -in particular the time of its termination—could be verified with a precision of a few days. The accuracy and reproducibility of the concentration profile was proven based on multiple investigations of single hairs. An individual hair growth rate of 0.55 mm/day was determined with a relative standard deviation of 8% by comparison of concentration profiles in hairs collected after a time span of 165 days. # 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Liquid chromatography–tandem mass spectrometry; Drug monitoring; Hair analysis; Segmentation; Antipsychotic drugs; Clozapine

1. Introduction The identification of drugs of abuse in hair is a wellestablished routine procedure in workplace testing, driving licensing, clinical compliance control and a number of forensic issues (e.g. drugs abstinence control, evaluation of drug induced diminished responsibility and drug facilitated crimes). On the other hand, the lack of correlation between dosage and hair concentration, influences of hair colour and treatment, a restricted reproducibility of analyses caused by heterogeneous specimens and the potential impact of external contaminations are undisputed limitations of this technique. The suitability of hair analysis to the identification of pharmaceutical substances depends on its chemical properties. Basic and lipophilic drugs (e.g. cocaine, clenbuterol) are well incorporated into hair and less susceptible to wash-out effects.

* Tel.: +49 89 54308 135; fax: +49 89 54308 134. E-mail address: [email protected] (D. Thieme). 0379-0738/$ – see front matter # 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.forsciint.2006.04.015

Clozapine in particular is well suitable for hair analysis [1]. The detection of the parent substance in concentrations up to 59.2 ng/mg [2] and a potential confirmation by its desmethyl metabolite [3,4] were reported. Hair colour appears to be an important parameter for the incorporation rate of clozapine into hair, indicating a high melanin binding of the drug. Moreover, a comparatively good correlation between dosage and hair concentration was reported [5]. Hair segmentation to elucidate the detailed long-term drug history was primarily focused on therapy control of psychiatric patients, e.g. detection of amitriptyline [6], antidepressants and antipsychotic drugs [2], benzodiazepines [7], chlorpromazine [8], clozapine[4], or haloperidol [9,10], other attempts were devoted to the identification of chloroquine [11], piritramide [12] and selegeline compliance control by identification of its metabolites [13]. The use of hair segmentation to receive detailed kinetic information is restricted by substance concentration in hair and corresponding detection limits. Typical hair concentrations range from 1 pg/mg to several ng/mg, involving substance

D. Thieme, H. Sachs / Forensic Science International 166 (2007) 110–114

amounts of 20–100 mg hair. Typical segment lengths are greater than 1 cm of an aligned hair strand, representing an average drug administration time window of 1 month. In a case of the occurrence of characteristic health problems (dizziness, somnolence, unconsciousness, stomach-ache, swollen tongue, speech disorders, apoplectic stroke, circulatory failure, diarrhoea, constipation [14]) amongst at least 46 employees of a service company, an unauthorized long-term administration of clozapine was suspected. Two main episodes of apparent intoxications symptoms, medical consultations and hospitalisations were observed during a time period of 1 year. Therefore, hair testing was undertaken to collect retrospective evidence of poisoning. Clozapine was detected in 24 of the hair samples at concentrations up to 1400 pg/mg. The main goal of the fine segmentation of hair was the accurate differentiation of individual intervals of drug administration and the elucidation of its termination, which was of great importance for the legal assessment of the case. The use of single hairs proved to be essential to overcome statistical uncertainties resulting from unequal growth rates and alignment of individual hairs in hair bundles. 2. Experimental 2.1. Hair sample preparation The following data were obtained from black hair samples of a 35 years old female victim (Asian ethnicity). In the selected case, a second sample was taken after a time span of 165 days. Hair samples were originally collected according to the standard procedure for drug testing, i.e. by cutting a hair strand close to the root and subsequent fixation. Typical initial weights for one analysis were in the order of magnitude 50 mg hair. Hair samples were decontaminated by 5 min agitation in a gas-tight tube with 5 mL petroleum benzene (boiling range to 40 8C, Merck), dried and cut into pieces of 1–2 mm length. After adding 100 ng of the internal standard (MPPH, 5-(4methylphenyl)-5-phenyl hydantoine, research grade, Serva), the hair particles were extracted by 3 h ultrasonification at 55 8C with 3 mL of methanol (Merck, for chromatography). A volume of 1.5 mL of this extract was evaporated and reconstituted with 100 mL of mobile phase. The initial hair segmentations were carried out using 3 cm segments of the hair strand. Afterwards, the amount of hair was reduced to individual hairs, segmented into pieces of 2.5 and 1 mm, respectively. The segmentation of individual hairs required a fixation of the fibre using adhesive tape. Due to the low total amount of hair sample, the mass of single snippets could not be

111

weighted by conventional laboratory devices. Hair concentrations were obtained by converting the length of a segment using an average mass of 6.4 mg/mm (estimated for the respective hair sample). The resulting hair particles are transferred into vials, containing 5 ng of the internal standard (MPPH) in 30 ml of a mixture of water and methanol (50/50, v/v). After three hours of ultrasonification at 55 8C, the vials are acclimatised to ambient temperature and analysed by LC–MS. 2.2. Instrumental analysis All analyses were carried out using an Agilent 1100 LC system (binary pump and autosampler) coupled to an API 4000 mass spectrometer (Applied Biosystems), equipped with a Turbo-Ion-Spray (ESI) source. The optimum ionisation of clozapine (free base, Sandoz) was achieved in positive mode using the parameters described in Table 1. Owing to the high number of individual samples, a rapid chromatographic separation was required. The application of a Synergy Polar-RP (Phenomenex, 75 mm 2.0 mm, 4 mm particle size) column provided a sufficient retention of all analytes under isocratic conditions at ambient temperature. The mobile phase was a 2 mM ammonium acetate buffer (ACS certified, Baker) in a mixture (50/50, v/v) of water (for chromatography, Merck) and acetonitrile (gradient grade, Baker). The mobile phase flow rate was set to 700 mL/min, compatible with a source temperature of 650 8C and source gas flow settings (nitrogen as sprayer and heater gas) of 50 psi. The injection volume was 10 mL. 2.3. Quantitation The accuracy of the quantitative results is mainly governed by parameters other than the conventional uncertainty of analytical processes. Two major factors contribute to the potential quantitative variance: the unknown recovery from hair matrix and the uncertainty of the exact amount (length) of single hair segments. The former represents a systematic error, which is likely to be equal for each individual sample and does not significantly influence concentration profiles or metabolite ratios. The masses of individual pieces were estimated by division the weight of an intact hair by the number of apparently equal segments. The significant inaccuracy of the fine segmenting, possible inhomogeneities of individual hairs and the lacking possibility to control the weight of hair segments results in an estimated statistical error of 20% (referred to the most frequently used 2.5 mm segments). This is supposed to override all other analytical and technical uncertainties by far.

Table 1 Optimum ionisation and fragmentation conditions for clozapine, norclozapine and MPPH

Clozapine Clozapine (qualifier) Norclozapine MPPH

Precursor ion (Da)

Product ion (Da)

Declustering potential (V)

Collision energy (V)

327.3 327.3 313.2 267.1

270.2 192.1 270.2 196.1

91 91 91 71

31 59 31 29

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Fig. 2. Conventional clozapine concentration profile, obtained from a hair strand cut into 3–5 cm pieces (50 mg each). A concentration maximum is observed in the 6–9 cm segment of the hair strand.

Fig. 1. Fast chromatographic separation of clozapine (RT = 0.64), norclozapine (RT = 0.55) and MPPH (int. std. RT = 0.69, not shown) in a 2.5 mm segment of a hair sample (total weight approximately 16 mg). Comparison of a positive segment (concentration of clozapine 17 pg/mg, equivalent to 90 fg on column, S/N > 24, lower window) and a blank, corresponding to samples ‘1’ and ‘0’ in Fig. 6.

Fig. 3. Comparison of clozapine concentration profiles obtained from two individual hairs collected 165 days after the first hair strand (compare Figs. 4 and 5). Both profiles are in good temporal coincidence, while absolute concentrations differ significantly.

The calibration was performed in a range of 1–5 pg (total amount of clozapine per segment). An appropriate linearity of the calibration is indicated by a regression coefficient better than 0.996. The semi-quantitative extrapolation ranged from 0.1 pg (corresponding to a signal-to-noise ratio of 11) to a maximum of 37 pg (at an intensity of 2 104 cps, positively within the linear detector range). The chromatographic performance is demonstrated in Fig. 1 by comparison of a positive hair segment with a blank segment (sample identity as denoted in Fig. 6). 3. Results and discussion 3.1. Concentration profiles The examination of 3–5 cm pieces of a hair strand indicates only a vague concentration maximum around 9 cm (Fig. 2). The comparison with analytical results, obtained from 2.5 mm segments of single hairs (Figs. 3–5) reveals some distinct and reproducible particularities: There are at least five different sharp concentration maxima, confirmed by a total number of seven individual hair profiles.

Fig. 4. Comparison of clozapine concentration profiles obtained from 2.5 mm segments of four individual hairs. All concentration profiles show a characteristic pattern of concentration maxima. The peak concentrations are influenced by the random collection of the segments, uncertainty of total sample amount and local hair characteristics.


Fig. 5. The reduction of segment sizes to 1 mm (corresponding to a time period of approximately 2 days) reveals a clear bimodal shape of the first peak and is in good accordance to the data obtained from 2.5 mm segments (compare segment number 1–12, Fig. 4).

The first (i.e. closest to the root) maximum exhibits a characteristic peak shape of a maximum modified by leading and tailing shoulders. Local peak concentrations of clozapine in the respective segments are accordingly higher than averages obtained from longer segments. The location (distance from root) of the concentration maxima shows a very good reproducibility, while absolute concentrations ratios between the peaks may vary significantly. The first concentration maximum was shifted in the 165 days between both sample collections by 9.1 cm. This indicates a relatively high individual growth rate of 0.55 mm/day (1.65 cm/month). Moreover, the variation of growth between individual hairs appears to be unexpectedly low. Estimation of the distance between the first and the fifth concentration maximum of each of the individual hairs results in an average of 10.1 cm and a standard deviation of 7.2%. In contrast to this high reproducibility of the qualitative profile, there are some obvious and significant deviations of quantitative results. A comparison of corresponding segments of different hairs may well exhibit different concentration ratios, which is most likely due to variations of an individual hair structures (e.g. melanin granules). These quantitative variations and the heterogeneity of hairs within a strand (i.e. the presence of 1% of non-growing telogenic hair) requires a repetition of hair profiling for confirmation. The concentration profile of clozapine is paralleled by the corresponding time course of its metabolite norclozapine. The overlay of both time courses (normalised to the respective maximum values, Fig. 6) shows a good match of both curves. This is in good accordance to the expectations, because the resolution of 2.5 mm is equivalent to a time between adjacent segments of 5 days and is therefore larger by far than the plasma half life of clozapine (14 h, 5–60 h) [14]).

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Fig. 6. Overlay of clozapine and norclozapine (normalised to clozapine) concentration profiles. The results are based on a 2.5 mm segmentation of a single hair from the second sampling. There is no obvious time shift between both concentration profiles, which is in good accordance to the short half life of clozapine. The labels ‘0’ and ‘1’ signify the hair segments corresponding to the chromatographic data as shown in Fig. 1.

3.2. Resolution Hair segment lengths were examined in a range between 1 mm and 3 cm length showing consistent qualitative results. The optimum size of a segment depends on the concentration and detection limits of the target analytes. If the analytical sensitivity is sufficiently high, a segment size of 3–5 mm appears to be an adequate compromise between resolution and reproducibility. Smaller segments may be useful, if the time of a single administration is more relevant than quantitative consistency between adjacent segments. 3.3. Relevance of contamination and diffusion Examination of the concentration alteration at the descending sections of the concentration profile (i.e. after termination of drug administration, e.g. first four segments in Fig. 4), suggests an average reduction of the hair concentration in adjacent 1mm segments by a factor of 3–4. This corresponds to an estimated incorporation half life of the drug in hair of 0.8 days, which is in good agreement to the elimination half life of clozapine in blood. This suggests that the incorporation of clozapine is closely related to blood concentration and it is not likely to be induced by sebum or sweat. Moreover, a potential influence of external contaminations or significant amounts of diffusion of clozapine along the concentration gradient can be excluded, due to the occurrence of sharp and reproducible concentration maxima. 4. Conclusion The diagnostic value of segmental analyses of hair samples for investigations of the drug history is undisputed, e.g. to investigate drug history [15] or treatment compliance in patients [7,13]. However, the accuracy of this information is so far restricted by the detection limits, requiring relatively large

114


amounts of hair. Moreover, the use of bundles of hair generates random uncertainties due to the misalignment of individual hairs. High resolution single hair segmentation may reveal accurate information on drug administration kinetic. Segments of single hair may be downsized to 1 mm length if hair concentration and detection limits provide so. The resulting concentration profiles proved to be highly reproducible and a time resolution of a few days may be achieved. The appearance of sharp concentration maxima in the clozapine hair profiles demonstrates that external contamination and diffusion processes do not lead to concentration alterations. A second sampling after 165 days showed consistent time course. An individual growth rate of 1.65 cm/month may be estimated from superposition of both concentration profiles. The generalisation of this approach is certainly restricted, attempts to profile clozapine and other antipsychotic drugs in hair of other individuals showed a potential influence of external contamination and/or wash-out effects. In general, the accomplishment of the procedure depends on the chemical properties of the compound in combination with its specific hair incorporation rate and respective results need a careful and case related interpretation.

[4] [5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13]

References [1] B. Ahrens, G. Rochholz, H.W. Sachs, H. Schutz, Detection of clozapine in hair after 1 years burial in soil grave, Arch Kriminol 196 (1995) 138. [2] M. Shen, P. Xiang, H. Wu, B. Shen, Z. Huang, Detection of antidepressant and antipsychotic drugs in human hair, Forensic Sci Int 126 (2002) 153. [3] W. Weinmann, C. Muller, S. Vogt, A. Frei, LC–MS–MS analysis of the neuroleptics clozapine, flupentixol, haloperidol, penfluridol, thioridazine,

[14]

[15]

and zuclopenthixol in hair obtained from psychiatric patients, J Anal Toxicol 26 (2002) 303. M. Rothe, Math.-Nat Fakulta¨t, Humboldt Universita¨t, Berlin, 1997. V. Cirimele, P. Kintz, O. Gosselin, B. Ludes, Clozapine dose-concentration relationships in plasma, hair and sweat specimens of schizophrenic patients, Forensic Sci Int 107 (2000) 289. F. Pragst, M. Rothe, J. Hunger, S. Thor, Structural and concentration effects on the deposition of tricyclic antidepressants in human hair, Forensic Sci Int 84 (1997) 225. R. Kronstrand, I. Nystrom, M. Josefsson, S. Hodgins, Segmental ion spray LC–MS–MS analysis of benzodiazepines in hair of psychiatric patients, J Anal Toxicol 26 (2002) 479. H. Sato, T. Uematsu, K. Yamada, M. Nakashima, Chlorpromazine in human scalp hair as an index of dosage history: comparison with simultaneously measured haloperidol, Eur J Clin Pharmacol 44 (1993) 439. M. Nakano, T. Uematsu, H. Sato, K. Kosuge, M. Nishimoto, M. Nakashima, Using ofloxacin as a time marker in hair analysis for monitoring the dosage history of haloperidol, Eur J Clin Pharmacol 47 (1994) 195. T. Uematsu, H. Matsuno, H. Sato, H. Hirayama, K. Hasegawa, M. Nakashima, Steady-state pharmacokinetics of haloperidol and reduced haloperidol in schizophrenic patients: analysis of factors determining their concentrations in hair, J Pharm Sci 81 (1992) 1008. U. Runne, F.R. Ochsendorf, K. Schmidt, H.W. Raudonat, Sequential concentration of chloroquine in human hair correlates with ingested dose and duration of therapy, Acta Derm Venereol 72 (1992) 355. D. Thieme, H. Sachs, Progress in forensic toxicology by application of liquid chromatography–mass spectrometry, Anal Chim Acta 492 (2002) 171. R. Kronstrand, J. Ahlner, N. Dizdar, G. Larson, Quantitative analysis of desmethylselegiline, methamphetamine, and amphetamine in hair and plasma from Parkinson patients on long-term selegiline medication, J Anal Toxicol 27 (2003) 135. R.J. Flanagan, E.P. Spencer, P.E. Morgan, T.R.E. Barnes, L. Dunk, Suspected clozapine poisening in the UK/Eire, 1992–2003, Forensic Sci Int 155 (2004) 91–99. K.M. Clauwaert, J.F. Van Bocxlaer, W.E. Lambert, A.P. De Leenheer, Segmental analysis for cocaine and metabolites by HPLC in hair of suspected drug overdose cases, Forensic Sci Int 110 (2000) 157.


A distinct Y-STR haplotype for Amelogenin negative males characterized by a large Yp11.2 (DYS458-MSY1-AMEL-Y) deletion Yuet Meng Chang a,*, Revathi Perumal a, Phoon Yoong Keat a, Rita Y.Y. Yong b, Daniel L.C. Kuehn c, Leigh Burgoyne c b

a Forensic DNA Laboratory, Department of Chemistry, Petaling Jaya, Malaysia Defence Medical and Environmental Research Institute, DSO National Laboratories, Singapore, Singapore c School of Biological Sciences, Flinders University, Adelaide, Australia

Received 10 September 2005; received in revised form 16 April 2006; accepted 21 April 2006 Available online 9 June 2006

Abstract The use of STR multiplexes with the incorporated gender marker Amelogenin is common practice in forensic DNA analysis. However, when a known male sample shows a dropout of the Amelogenin Y-allele, the STR system falsely genotypes it as a female. To date, our laboratory has observed 18 such cases: 12 from our Y-STR database and six from casework. A study on 980 male individuals in the Malaysian population using the AmpFlSTR1 Y-filerTM has revealed a distinct Y-chromosome haplotype associated with the Amelogenin nulls. Our results showed that whilst the Amelogenin nulls were noticeably absent among the Chinese, both the Indians and Malays exhibited such mutations at 3.2 and 0.6%, respectively. It was also found that the Amelogenin negative individuals predominantly belonged to the J2e lineage, suggesting the possibility of a common ancestor for at least some of these chromosomes. The null frequencies showed concordance with the data published in Chang et al. (Higher failures of Amelogenin sex test in an Indian population group, J. Forensic Sci. 48 (2003) 1309–1313) [1] on a smaller Malaysian population of 338 males which used a Y-STR triplex. In the current study, apart from the absence of the Amelogenin Y-locus, a complete absence of the DYS458 locus in all the nulls was also observed. This study together with the 2003 study has indicated a similar deletion region exists on the Yp11.2 band in all the 18 Ychromosomes. Using bioinformatics, this deletion has been mapped to a region of at least 1.13 Mb on the Yp11.2 encompassing the Amelogenin, MSY1 minisatellite and DYS458 locus. Further, the Y-filerTM haplotypes revealed an additional null at Y-GATA H4 in two of the Indian males presented here. # 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Amelogenin (AMEL); Amelogenin Y-allele (AMEL-Y); Null allele; Haplotype; Deletion; Indians; Malays; Chinese; Malaysia

1. Introduction In forensic science, gender is commonly determined through PCR-based assays that target a small region of the X–Y homologous Amelogenin gene. This sex-typing test is easily performed using the AMEL 106/112 bp primers that are routinely incorporated in standard forensic STR multiplexes and generates two amplicons of 6 bp difference, the longer product being the Ychromosome amplicon. Dropout of the AMEL-X (106 bp) has been shown to be due to a mutation in the primer-binding region of the gene on the X-chromosome [2], though this will not cause gender mistyping as the Y-allele is still present. However, if the * Corresponding author. Tel.: +60 3 79853836; fax: +60 3 79581173. E-mail addresses: [email protected], [email protected] (Y.M. Chang). 0379-0738/$ – see front matter # 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.forsciint.2006.04.013

AMEL-Y has dropped out, the STR system will falsely genotype the sample as a female. The Forensic DNA Laboratory of the Department of Chemistry in Malaysia has observed a number of such cases from the Malaysian population. The occurrence of AMEL-Y negative males in the Malaysian population was first reported in a study on 113 Malays, 113 Chinese and 112 Indians using a 3-loci Y-STR multiplex in 2003 [1]. Recently, we carried out Y-STR haplotyping on a larger male population comprising of 334 Malays, 331 Chinese and 315 Indians using a 16-loci multiplex, the Y-filerTM by Applied Biosystems (Foster City, CA, USA). This megaplex simultaneously amplifies nine European minimal loci (DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS385a/b), two SWGDAM-extended loci (DYS438, DYS439) and six new additional loci (DYS456, DYS458, DYS635 or YGATA C4, Y-GATA H4, DYS437 and DYS448).

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Y.M. Chang et al. / Forensic Science International 166 (2007) 115–120

To date, our laboratory has observed 18 AMEL-Y negative males: 12 from our Y-STR database (10 Indians, 2 Malays) and 6 from casework (5 Indians, 1 Malay). We describe here discordant observations where the AMEL Y-locus, along with the DYS458 locus, was completely absent in the 18 Ychromosomes. In all these cases, we report a failure in the sex genotyping of the male individuals. Except for four null males, the haplogroup or haplogroups where the deletion took place were also ascertained. Based on the results obtained, a brief discussion of the plausible origins of the nulls is included.

Integrated System (IS) software of the Liquidchip workstation, and data analysis with Microsoft1 Excel. A two-level screen was employed: the first screen classified samples into major clades following the YCC 2003 phylogenetic tree [3], whilst the second screen delineated specific haplogroups within each clade:

2. Materials and methods

J2e was identified by its Y-SNP signature of M89T/M9C/ M304C/M172G/M241A [4]; D* by M168T/M89C/M96G/M130C/M145A/M15(D)/ M55T; F* by M89T/M9C/M304A/M201G/M52A/M170A/M253C/ P37T/M26G.

2.1. Collection and isolation of genomic DNA

3. Results

Blood of 980 unrelated males with self-reported ethnicity from the three main ethnic populations in Malaysia was stained on FTA1 cards (Whatman1, USA) and a 1.2 mm disc was excised from each card and purified in situ using standard protocols. For the casework samples, Chelex extraction was carried out followed by quantification using QuantifilerTM Real-Time PCR (Applied Biosystems, Foster City, CA, USA).

Based on the Identifiler1 STR results, 18 male individuals exhibited a female genotype, indicated by the absence of the 112 bp AMEL-Y peak. These subjects were coded N1–N18, with the first six described previously [1]. Of the 18 AMEL-Y negative males, 14 were from the Indian group whilst the remaining 4 were from the Malay group. Interestingly, no discordant results were detected in the Chinese group. Subsequent amplification of the 16 Y-filerTM Y-STR loci provided more definitive male haplotypes (Table 1), confirming that the 18 discordant samples were from true male individuals. Preliminary haplogrouping (Hg) studies using Y-SNPs on 14 of the AMEL-Y nulls showed that 12 belong to Hg J2 (N1– N4, N7, N8, N10–N15), with one Hg D (N5) and one Hg H (N9) (personal communication from M.A. Jobling, 2006, see Table 1). The haplogroups for the other four nulls from casework (N6, N16–N18) could not be determined due to insufficient quantities. Recently, 12 of the population database null samples were tested for haplogroups using a different panel of Y-SNP markers. The results showed that 10 out of the 12 nulls (N1–N4, N7, N8, N10–N13) fall under the same Y-chromosome haplogroup which is J2e, with the other two nulls under Hg F* (N9), and Hg D* (N5) (see Table 1). It is interesting to note that the null sample N9 has been typed as H in the first system but F* in the second system. The difference in the haplogroups obtained for N9 is likely due to the M52 marker, which is the critical Y-SNP marker that differentiates Hg H from other haplogroups. The ancestral state of M52 is A, whilst the derived state that defines H is C. Both H and F* samples have the common signature of M89T/ M9C/M304A. For finer differentiation, H will have M52C/ M170A/M201G, whilst F* will have M52A/M170A/M201G. The Malaysian null N9 was confirmed to have M52A as standards from NIST (SRM2395, National Institute of Standards and Technology, USA) with known M52A status were analysed concurrently during the haplogrouping analysis. In addition, there are samples from the Singaporean database that display the alternative status, M52C (data not shown). Therefore the technical performance of M52A and M52C has been validated in the present Y-SNP assay system.

2.2. Y-STR haplotyping Amplification with the Y-filerTM multiplex was performed directly on the purified discs using 20 ml reaction volume following recommendations by the manufacturer on a GeneAmp1 PCR System 9700 (Applied Biosystems). For FTA1 samples, a single purified disc was used in the PCR with reduced (27) cycles. For Chelex extracts, approximately 1– 1.2 ng per assay was used. The amplified products were electrophoretically separated on an ABI Prism1 3100 Genetic Analyzer (Applied Biosystems) using an injection time of 10 s at 3 kV; whilst POP-4TM, loading mix and other reagents were according to the manufacturer’s instructions. Following separation, the fluorescent fragments were analyzed using the Genescan1 and Genotyper1 programs (Applied Biosystems). Amplification with the AmpFlSTR1 Identifiler1 STR system (Applied Biosystems, Warrington, UK) was also carried out for the null samples following recommendations by the manufacturer prior to Y-STR haplotyping. 2.3. Y-SNP haplogrouping Y-SNP haplogrouping was carried out with a beta test version Y-SNP kit manufactured by Marligen Biosciences (Maryland, USA). A microbead platform was employed. YSNP fragments amplified by multiplex PCR were labelled with a fluorescent tag. The labelled products were hybridized to YSNP-specific oligonucleotides immobilised onto individually colour-coded beads. The bead mixes were analysed on a Liquidchip workstation (Qiagen, Germany), which delineated the spectral address of each bead and the amount of fluorescent tag per bead. Fluorescent data acquisition was done with the

Table 1 Y-STR and haplogroup results of the 18 AMEL-Y negative males typed with Y-filerTM

Y.M. Chang et al. / Forensic Science International 166 (2007) 115–120 117

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4. Discussion 4.1. Amelogenin-Y null frequencies The data presented here was in agreement with the frequency data published in a 2003 study [1] on a smaller Malaysian population using a Y-STR triplex. However, this larger study has provided more information although still not complete, on the nulls and their possible origin/divergence. The AMEL-Y negative males were mostly from one migrant group which is the Indian group (3.2%), with a small proportion in the native Malay group (0.6%) and noticeably none in the Chinese group, the other major migrant group. A higher AMEL-Y dropout was similarly noted in several global population groups [1,5–11, and personal communication from M.A. Jobling (2005)]. Overall, there is a notably higher frequency of this mutation in males of Indian or Sri Lankan origin and a much lower frequency in a few Caucasian population groups (Table 2). It is now evident that there is a prominent lineage associated with the AMEL-Y null that may have spread from the Indian subcontinent, with other similar mutations cropping up sporadically elsewhere in the world. The conspicuous absence of the AMEL-Y null among the Chinese in Malaysia and in other reported global populations thus far poses an interesting question: how is the AMEL-Y null propagating through a population? What is so different about the Indian and Sri Lankan populations that they have much higher frequencies of AMEL-Y nulls than other populations?

mutation. In contrast, the Y-specific minisatellite MSY1 locus, located on the same Yp11.2 band as the AMEL-Y locus, has been shown to be absent in six previously studied deletion males [1]. Recently, Lattanzi et al. [10] used deletion mapping to locate the distal break-point for this interstitial deletion that encompasses the AMEL-Y locus and confirmed that the lesion spanned approximately 2.5 Mb on the pericentromeric region of the short arm of the Y-chromosome. The Y-filerTM haplotypes associated with this AMEL-Y allele deletion mutation in the 18 males consistently showed an absence of the DYS458 locus, indicating that both loci were similarly deleted. DYS458, a polymorphic complex tetranucleotide (GAAA) repeat locus has seven alleles in the Y-filerTM allelic ladder ranging from 14 to 20, with allele 16 being the most common allele observed in both the Indian (27.0%) and Malay (32.1%) groups in Malaysia [12]. Using published primer sequences [13–16] and the Ensembl human genome browser (http://www.ensembl.org/Homo_sapiens/index.html), the map locations of the 16 Y-filerTM loci, the AMEL-Y, MSY1, SRY and DYZ1 were plotted. DYS458 and the AMEL-Y loci differed by 1.13 Mb on the short arm of the Y-chromosome, with the minisatellite MSY1 located in between the two loci, and 0.73 Mb from the AMEL-Y locus. This indicated a large deletion in the Yp11.2 band in all the affected 18 Y-chromosomes which includes Amelogenin, the MSY1 minisatellite and the DYS458 locus, and are all within the boundaries of the deletion mapped by Lattanzi et al. [10] as shown in the schematic map (Fig. 1). 4.3. Possible origins of the AMEL-Y null

4.2. A limited Yp11.2 deletion (DYS458-MSY1-AMEL-Y) on the 18 Y-chromosomes Previous studies using alternative sets of AMEL primers targeting different regions of the gene have demonstrated that the failure of the Amelogenin sexing test is commonly due to a large lesion encompassing the AMEL copy on the Y-chromosome [1,6,10]. Other suggested sex-markers on the Y-chromosome which are located outside the AMEL gene have also been tested, such as the SRY gene (located on Yp11.31) [5,8–10], and the DYZ1 locus (located on Yq12) [6], and are not commonly involved as amplifications using the primers for these two loci demonstrated that they were intact in males carrying this deletion Table 2 Summary of AMEL-Y null frequencies in global population groups Population

No. of nulls/ individuals studied

Frequency (%)

Reference

Sri Lanka Austria India (general) Italy Israel South India England Spain Malaysian Indians Malaysian Malays

2/24 5/28182 5/270 1/13000 1/96 1/100 2/2000 1/1000 10/315 2/334

8.3 0.018 1.9 0.008 1.0 1.0 0.1 0.1 3.2 0.6

[5] [8] [9] [10] [11] Pers. comm. Pers. comm. Pers. comm. Current study Current study

Note: Pers. comm.: personal communication from M.A. Jobling (2005).

There are generally three primary mechanisms for any mutation to transmit in the human genome: (1) founder effect/ genetic drift, (2) genomic processes (normal mutations) and (3) selection forces (at the level of the individual, or physical and/ or social and/or other bases). It seems unlikely that the frequency of the deletion has arisen as a consequence of natural selection on these Ychromosomes, as there are no distinct classes of related Y-STR haplotypes observed to go with the deletion on Yp11.2 band in the two affected ethnic populations harbouring this deletion (see Table 1). All 18 males’ deletion consistently included the same three null loci of AMEL-Y-MSY1-DYS458 which are all within a region of 1.13 Mb, suggesting that either a single ancestral deletion event involving the three null loci or three random deletion events had occurred on these Y-chromosomes. Y-SNP haplogrouping results revealed that there are at least three different haplogroups in the 18 males carrying the AMELY deletion. Out of the 14 nulls tested for haplogrouping, 12 (10 Indians and 2 Malays) were from haplogroup J2, 10 of these are now tested to belong to sub-clade J2e in the current study. The remaining Indian null belongs to haplogroup F*, which is ancestral to the J2e chromosomes according to the YCC tree [17], with the other Malay null (N5) being from haplogroup D*. The data observed so far indicates a founder event for the J2 deletion some time ago but we do not know the age of this deletion. The other null from a Malay (N5) belonging to haplogroup D* may represent an independent event happening


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Fig. 1. Schematic representation of human Y-chromosome map. (A) Approximate locations of each of the 16 Y-STR loci from Y-filerTM in addition to the locations of AMEL-Y, MSY1, SRY, and DYZ1. The locations were determined by performing database searching with published primer sequences. Immediately below the approximate scale are the four regions susceptible to deletion. Region I is the AMEL-Y deletion; Regions II, III, and IV, are the azoospermia factor related regions, AZFa, b, and c, respectively [22–24]. Locations marked with * represent double loci, e.g. DYS385a,b at 19.19 Mb. (B) An expanded view of the AMEL-Y-MSY1DYS458 contigs of the Yp11.2 band with a more accurate scale. The deletion mapped by Lattanzi et al. [10] begins at 6.44 Mb and ends around 9 Mb. Contig accession numbers from the Ensembl Genome browser are included.

sporadically elsewhere but may also involve similar mechanisms to the J2’s chromosomes. The Y-chromosome J2 lineage (defined by mutation M172) is approximately 15,000 years old [4] and expanded throughout the Middle East, Central Asia, the Mediterranean and India about 7,500 years ago [18]. Currently, we do not have the haplogroup results of the larger Indian population in the Malaysian database, however haplogroup J2 is said to exist in approximately 9% of the population in India whilst haplogroup F* (defined by mutation M89) is approximately 5% [19]. An analysis of the average allele repeat number and allele variance observed at certain Y-STR loci (DYS19, DYS389I, DYS390, DYS391, DYS392, DYS393 and DYS439; Table 1) for the J2e nulls in this study corresponds to that reported by Cinnioglu et al. [20] for the J2e haplogroup. It has recently been shown that the absence of Y-STR products from certain loci in the q-arm of the Y-chromosome can inadvertently reveal infertile males in the population [21]. Interestingly, two out of the 14 Indian AMEL-Y nulls also showed nulls at the Y-GATA H4 locus (located on Yq11.221, see Fig. 1), suggesting a more recent deletion around the AZFb

region, which corresponds with one of the three major ‘‘hotspots’’ defined on the long arm of the Y-chromosome responsible for azoospermia (see Table 1 and Fig. 1). Alleles for the Y-GATA H4 locus range from 8 to 13, with allele 12 being the most common allele observed in both the Malay (42.0%) and Indian (51.8%) groups [12]. Due to a lack of genotype– phenotype analysis, it is not known whether the deletions reported here have some compensating advantage or are immune in some way from the expected semen impairment. The 2.5 Mb deletion defined by Lattanzi et al. [10] in the Italian population was found in one infertile oligozoospermic male, one pre-natal male, and their respective fathers. Given that both fathers had produced their sons naturally, they were assumed to be fertile despite the presence of the AMEL-Y deletion, and the infertility of the test subject is therefore presumed to have had other origins [10]. Even though AMEL-Y negative males seem to have multiple origins in global populations, the haplogroup results for the Indian nulls have so far indicated an ancestral J2e lineage, and the presence of an additional null at Y-GATA H4 in two of the affected Indian males may be worth investigating further for

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any potential link to the AMEL-Y deletion. Future work should include estimating the age of the deletion mutation with more in-depth mapping, genotype–phenotype analysis or comparison of more haplotypes between the nulls from similar lineages and haplogrouping from the Malaysian population database. Determining the DNA sequence across the deletions would also be potentially valuable to further investigate the actual mutational mechanisms at work. 5. Conclusion The failure rate of the Amelogenin sexing test has a consequence in the forensic scenario in Malaysia and any nation with a sizeable Indian population. Whenever a casework stain shows an AMEL-Y null it cannot be assumed to be femaleorigin, and requires the additional determination of the Y-STR haplotype. The absence of the DYS458 locus and/or the MSY1 minisatellite, in the presence of other Y-STR loci, would then serve as a stronger indication of the AMEL-Y deletion. To the forensic community, although the frequency of the AMEL-Y null is relatively low in population groups other than Indians, gender testing in human identification needs high reliability and therefore a sex genotyping test based on Amelogenin locus alone is insufficient for casework. In this respect, routine YSTR haplotyping using kits like Y-filerTM can provide a quick and practical means to confirm males carrying this chromosomal aberration. Acknowledgements The authors gratefully acknowledge Prof. M.A. Jobling for the personal communications and the two expert reviewers for their helpful comments and suggestions. We would like to thank the Director-General and all staff of the DNA/Serology Laboratory, Forensic Division at the Department of Chemistry, Ministry of Science, Technology and Innovation, Malaysia. We also thank all the volunteers who have kindly donated their blood samples for this study. This study was supported by the Department of Chemistry, Ministry of Science, Technology and Innovation in Malaysia. References [1] Y.M. Chang, L.A. Burgoyne, K. Both, Higher failures of Amelogenin sex test in an Indian population group, J. Forensic Sci. 48 (2003) 1309–1313. [2] B. Shadrach, M. Commane, C. Hren, I. Warshawsky, A rare mutation in the primer binding region of the Amelogenin gene can interfere with gender identification, J. Mol. Diagn. 6 (2004) 401–405. [3] M.A. Jobling, C. Tyler-Smith, The human Y chromosome: an evolutionary marker comes of age, Nat. Rev. Genet. 4 (2003) 598–612. [4] P. Shen, T. Lavi, T. Kivisild, V. Chou, D. Sengun, D. Gefel, I. Shpirer, E. Woolf, J. Hillel, M.W. Feldman, P.J. Oefner, Reconstruction of patrilineages and matrilineages of Samaritans and other Israeli populations from Y-chromosome and mitochondrial DNA sequence variation, Hum. Mutat. 24 (2004) 248–260. [5] F.R. Santos, A. Pandya, C. Tyler-Smith, Reliability of DNA-based sex tests, Nat. Genet. 18 (1998) 103.

[6] P.E. Roffey, C.I. Eckhoff, J.L. Kuhl, A rare mutation in the Amelogenin gene and its potential investigative ramifications, J. Forensic Sci. 45 (2000) 1016–1019. [7] J. Henke, L. Henke, P. Chatthopadhyay, M. Kayser, M. Du¨lmer, S. Cleef, H. Poche, H. Felske-Zech, Application of Y-chromosomal STR haplotypes to forensic genetics, Croat. Med. J. 42 (2001) 292–297. [8] M. Steinlechner, B. Berger, H. Niedersta¨tter, W. Parson, Rare failures in the Amelogenin sex test, Int. J. Legal Med. 116 (2002) 117–120. [9] K. Thangaraj, A.G. Reddy, L. Singh, Is the Amelogenin gene reliable for gender identification in forensic casework and prenatal diagnosis? Int. J. Legal Med. 116 (2002) 121–123. [10] W. Lattanzi, M.C. Di Giacomo, G.M. Lenato, G. Chimienti, G. Voglino, N. Resta, G. Pepe, G. Guanti, A large interstitial deletion encompassing the Amelogenin gene on the short arm of the Y chromosome, Hum. Genet. 116 (2005) 395–401. [11] A. Michael, P. Brauner, Erroneous gender identification by the Amelogenin sex test, J. Forensic Sci. 49 (2004) 258–259. [12] Y.M. Chang, R. Perumal, P.Y. Keat, D.L.C. Kuehn, Haplotype diversity of 16 Y-chromosomal STRs in three main ethnic populations (Malays, Chinese and Indians) in Malaysia, Forensic Sci. Int. [Epub ahead of print]. [13] A. Hall, J. Ballantyne, The development of an 18-locus Y-STR system for forensic casework, Anal. Bioanal. Chem. 376 (2003) 1234–1246. [14] A.J. Redd, A.B. Agellon, V.A. Kearney, V.A. Contreras, T. Karafet, H. Park, P. de Knijff, J.M. Butler, M.F. Hammer, Forensic value of fourteen novel STRs on the human Y-chromosome, Forensic Sci. Int. 130 (2002) 97–111. [15] M.A. Jobling, N. Bouzekri, P.G. Taylor, Hypervariable digital DNA codes for human paternal lineages: MVR-PCR at the Y-specific minisatellite, MSY1 (DYF155S1), Hum. Mol. Genet. 7 (1998) 643–653. [16] A. Akane, H. Shiono, K. Matsubara, Y. Nakahori, S. Seki, S. Nagafuchi, M. Yamada, Y. Nakagome, Sex identification of forensic specimens by polymerase chain reaction (PCR): two alternative methods, Forensic Sci. Int. 49 (1991) 81–88. [17] The Y-chromosome consortium, A nomenclature system for the tree of human Y-chromosomal binary haplogroups, Genome Res. 12 (2002) 339– 348. [18] A. Nebel, D. Filon, B. Brinkmann, P.P. Majumder, M. Faerman, A. Oppenheim, The Y chromosome pool of Jews as part of the genetic landscape of the Middle East, Am. J. Hum. Genet. 69 (2001) 1095–1112. [19] S. Sengupta, L.A. Zhivotovsky, R. King, S.Q. Mehdi, C.A. Edmonds, C.E. Chow, A.A. Lin, M. Mitra, S.K. Sil, A. Ramesh, M.V. Usha Rani, C.M. Thakur, L.L. Cavalli-Sforza, P.P. Majumder, P.A. Underhill, Polarity and temporality of high-resolution Y-chromosome distributions in India identify both indigenous and exogenous expansions and reveal minor genetic influence of Central Asian Pastoralists, Am. J. Hum. Genet. 78 (2006) 202–221. [20] C. Cinnioglu, R. King, T. Kivisild, E. Kalfoglu, S. Atasoy, G.L. Cavalleri, A.S. Lillie, C.C. Roseman, A.A. Lin, K. Prince, P.J. Oefner, P. Shen, O. Semino, L.L. Cavalli-Sforza, P.A. Underhill, Excavating Y-chromosome haplotype strata in Anatolia, Hum. Genet. 114 (2004) 127–148. [21] T.E. King, E. Bosch, S.M. Adams, E.J. Parkin, Z.H. Rosser, M.A. Jobling, Inadvertent diagnosis of male infertility through genealogical DNA testing, J. Med. Genet. 42 (2005) 366–368. [22] F. Raicu, L. Popa, P. Apostol, D. Cimponeriu, L. Dan, E. Ilinca, L.L. Dracea, B. Marinescu, L. Gavrila, Screening for microdeletions in human Y chromosome-AZF candidate genes and male infertility, J. Cell. Mol. Med. 7 (2003) 43–48. [23] P.C. Patsalis, N. Skordis, C. Sismani, L. Kousoulidou, G. Koumbaris, C. Eftychi, G. Stavrides, A. Ioulianos, S. Kitsiou-Tzeli, A. Galla-Voumvouraki, Z. Kosmaidou, C.G. Hadjiathanasiou, K. McElreavey, Identification of high frequency of Y chromosome deletions in patients with sex chromosome mosaicism and correlation with the clinical phenotype and Y-chromosome instability, Am. J. Hum. Genet. 135 (2005) 145–149. [24] G. Vinci, F. Raicu, O. Popa, R. Cocos, K. McElreavey, A deletion of a novel heat shock gene on the Y chromosome associated with azoospermia, Mol. Hum. Reprod. 11 (2005) 295–298.


A new sensitive short pentaplex (ShoP) PCR for typing of degraded DNA C. Meissner a,*, P. Bruse a, E. Mueller c, M. Oehmichen a,b a

Department of Forensic Medicine, Medical University of Luebeck, Kahlhorststrasse 31-35, 23562 Luebeck, Germany b Department of Forensic Medicine, University of Kiel, Germany c Bundeskriminalamt, Wiesbaden, Germany Received 13 May 2005; received in revised form 18 April 2006; accepted 21 April 2006 Available online 30 June 2006

Abstract Analysis of short tandem repeat makers has become the most powerful tool for DNA typing in forensic casework analysis. Unfortunately, typing of DNA extracted from telogen shed hairs, bones buried in the soil or from paraffin-embedded, formalin-fixed tissue often reveals no results due to the degradation of DNA. The reduction in size of the target fragments by development of new primers and their combination in multiplex approaches open a new field of DNA analysis. Here we present a new sensitive short pentaplex PCR including the loci amelogenin, TH01, VWA, D3S1358 and D8S1179. Validation tests of our new method included sensitivity, mixtures, human specificity, artificial degradation of DNA by DNase I and case work analysis on a panel of different forensic samples. The detection limit was 12.5 pg of human DNA, and mixtures of 50 pg in a total of 1000 pg were clearly detectable and revealed complete profiles. Only DNA extracts of human primates displayed a few signals, whereas other animal, fungal or bacterial DNA showed no signals. Our method proved extremely valuable in the analysis of artificially degraded DNA and in forensic cases, where only poorly preserved DNA was available. This approach and other similar methods can aid in the analysis of samples where allelic drop out of larger fragments is observed. It is highly recommended to develop more of these multiplexes to improve poor quality DNA typing. # 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: DNA typing; Short tandem repeats; Multiplex PCR; Forensic casework

1. Introduction In the last decade, DNA typing of highly polymorphic STR (short tandem repeat) loci has become the most powerful tool for discrimination of individuals, because these loci are even stable in decomposed tissues [1]. In particular, the simultaneous amplification of multiple STR markers in the same PCR has found multiple applications even in cases with only minute amounts of DNA [2]. In these multiplex PCR assays usually fluorescent dyes are attached to the forward primer of different loci to allow discrimination of fragments of similar size [3]. The development of capillary electrophoresis enables the on-line detection of these labelled PCR amplicons with the advantage of high throughput, automatic operation and automated data acquisition [4]. Nevertheless there are a lot of forensic cases

* Corresponding author. Tel.: +49 451 500 2752; fax: +49 451 500 2760. E-mail address: [email protected] (C. Meissner). 0379-0738/$ – see front matter # 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.forsciint.2006.04.014

where DNA is highly degraded due to the quality of the sample itself [5] or environmental conditions [6,7]. These cases include skeletal remains buried in the soil [8], decomposed bodies [9], paraffin-embedded tissue [10] or shed telogen hairs [5]. The rate of decay of DNA depends to a large extend on the geochemical properties of the soil, the effects of the surrounding milieu, contamination with microorganisms and temperature [7,11,12]. Especially exposure of bone or teeth in damp environments seems to be crucial for successful DNA typing [6,13]. On the other hand, DNA degradation is reduced under permafrost conditions in arctic regions, facilitating analyses of remains up to 50,000 years old [11]. Nevertheless, ancient DNA extracted from bones up to more than 10,000 years old displays an average size between 100 and 150 bp and oxidative as well as hydrolytic damage making PCR amplification and DNA typing extremely difficult [11,14,15]. At worst, DNA can be degraded to such an extent that it is no longer suitable for demonstration of STR profiles [16]. Therefore, a lot of different approaches have been presented to

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improve the quality of DNA profiling of degraded DNA. These studies include the evaluation of different extraction methods [9], removal of special PCR inhibitors, as well as purification of extracts [17,18], a nested PCR method [19] and typing of standardized degraded DNA [12]. Recently an excellent review about the application of reduced size amplicons for reliable DNA typing of degraded DNA has been published. These miniplex PCRs are recommended in cases where allelic drop out and reduced sensitivity especially of larger alleles occurs [20]. So far, a few of these interesting miniplex PCRs have already been described for a variety of forensic samples [20,21] including shed telogen hairs [5]. Learning from lessons of degradation of DNA even over long periods of time we developed a multiplex PCR where none of the detectable alleles is more than 150 bp in length. Here we present a short pentaplex PCR (ShoP-PCR) approach which is highly suitable to obtain excellent results even in cases where DNA typing was unsuccessful using commercially available kits. 2. Materials and methods 2.1. Primer design Sequences of primers were designed using the Primer3 [22] and GeneFisher (http://bibiserv.techfak.uni-bielefeld.de/cgi-in/ gf_submit?mode=STARTUP&sample=dna) software. Forward primers were labelled with fluorescent dyes as shown in Table 1.

incubation at 37 8C for 5 min. The cycling profile of the ShoPPCR in a GeneAmp PCR system 2400 (Applied Biosystems, Darmstadt, Germany) was 95 8C for 11 min (initial incubation), 96 8C for 2 min, followed by 10 cycles of denaturation for 30 s at 94 8C, annealing for 30 s at 60 8C and extension for 45 s at 70 8C and then by 18–22 cycles of denaturation for 30 s at 90 8C, annealing for 30 s at 60 8C and extension for 45 s at 70 8C. This was followed by a final elongation step of 90 min at 60 8C. At the end of the PCR reaction, the temperature was kept at 4 8C. Ramping time between annealing and extension was carefully adjusted between 0.3 and 0.5 8C/s. 2.3. Signal detection One to two microliters of each PCR product was mixed with 0.5 ml GeneScan-400HD (ROX) internal lane standard (Applied Biosystems, Darmstadt, Germany) and 14.5 ml of deionized formamide (Sigma, Taufkirchen, Germany). The mixture was subjected to heat denaturation in the PCR thermocycler for 3 min at 96 8C. After cooling on ice the samples were injected electrocinetically for 5 s. Detection was performed on a 310 ABI Prism Genetic analyzer according to the manufacturers recommendations (Applied Biosystems, Darmstadt, Germany). Fragment sizes and amount of PCR products were determined automatically applying GeneScan Analysis Software 3.1 (Applied Biosystems, Darmstadt, Germany). 2.4. Validation procedures

2.2. PCR amplification Pentaplex PCR was carried out in a 10 ml reaction mix containing 20 mM Tris–HCl (pH 8.4), 50 mM KCl, 200 mM each dNTP (dATP, dGTP, dCTP, dUTP), 2.2 mM MgCl2, 500 mg/ml bovine serum albumin, 1% Tween 20, 200 nM each of amelogenin primer, 600 nM each of D8S1179 primer, 1000 nM each of vWA primer, 75 nM each of TH01 primer, 150 nM each of D3S1358 Primer, 1 U Platinum Taq DNA Polymerase (Invitrogen, Karlsruhe, Germany), 0.1 U UNG (MBI Fermentas, Leon-Rot, Germany) and a variable amounts of template DNA. To avoid contaminating PCR products samples were digested with UNG (Uracil-DNA Glycosylase) prior to amplification by

2.4.1. Primer specificity Buccal swabs were collected from 200 unrelated healthy volunteers and DNA was immediately extracted using the Chelex 100 method [23]. For comparison 200 human DNA profiles obtained by the ShoP-PCR were compared with profiles applying the SGM und PowerPlex 16 system of the same individuals. To test human specificity DNA from various animals (cat, dog, pig, horse, cow, mouse, rat, frog, fish, sheep, rabbit, guinea pig, goat, deer, black deer, fox, pigeon and herring) and the three closest related primates (gorilla, orangutan, chimpanzee) was isolated. DNA extraction was performed using the QIAamp

Table 1 Description, repeat number of allelic ladder components, allelic size range and primer sequences of the ShoP-PCR loci System

GenBank1 accession

Repeat numbers of allelic ladder components

Size range of allelic ladder components

Primers (50 ! 30 )

Labelled with

Amelogenin

3 bp difference

X: 79 bp, Y: 82 bp

7–18

83–127 bp

VWA

M25858

10–22

93–141 bp

TH01

D00269

4–9, 9.3, 10–11, 13.3

68–107 bp

D3S1358

11449919

12–20

113–145 bp

CCTTTGAAGTGGTACCAGAGCA (forward), GCATGCCTAATATTTTCAGGGAA (reverse) TTTTTGTATTTCATGTGTACATTCG (forward), TCCTGTAGATTATTTTCACTGTGG (reverse) GAATAATCAGTATGTGACTTGGATTGA (forward), GATGATAAATACATAGGATGGATGGA (reverse) GCCTGTTCCTCCCTTATTTCC (forward), AGGTCACAGGGAACACAGACTC (reverse) ACTGCAGTCCAATCTGGGTGAC (forward), GAAATCAACAGAGGCTTGCATG (reverse)

HEX

D8S1179

M55418 and M55419 GO8710

Sequences of the D8S1179 forward primer have been already published [38].

6-FAM HEX NED NED


Mini DNA kit (Qiagen, Hilden, Germany) and stored at 20 8C. Additionally, a panel of different bacterial or fungal DNA extracts were applied to proof human-specific annealing of primers. One nanogram DNA of each extract was subjected to PCR as described above. 2.4.2. Sensitivity and DNA mixtures Ten different dilutions of DNA extracts of blood were prepared with an amount of template of 100, 50, 25, 12.5 and 6.25 pg, respectively. The amount of template subjected to the mixture was determined applying the PicoGreen dsDNA Quantification Kit (MoBiTec, Goettingen, Germany) in a VersaFluorTM Fluorometer System (Bio-Rad, Munich, Germany) down to 0.025 ng and then diluted to 0.0125 and 0.00625 ng. Mixture samples (1:0, 19:1, 9:1, 4:1, 2:1, 1:1, 1:2, 1:4, 1.9, 1:19 and 0:1) were prepared of two different DNA extracts with a total input of 1 ng DNA and quantification was performed as described. 2.4.3. DNase I test To monitor successful DNA typing of degraded DNA a DNase I test was performed. High molecular weight DNA was extracted using the MasterPureTM DNA Purification Kit (Epicentre, Madison, WI, USA). Eighty micrograms of the extract were digested with 8 U DNase I in a 200 ml reaction mix applying the DNA-free kit (Ambion, Huntingdon, UK). An aliquot of 20 ml was taken after 0.5, 1, 2, 3, 4, 8, 15 and 30 min, respectively and reaction stopped by adding 4 ml of DNase Inactivation Reagent. 0.2 ml of degraded DNA was taken and subjected to a 10 ml PCR as described above. 2.5. Forensic casework At last our pentaplex approach was tested for suitability in forensic casework analysis. As an example eight poor quality DNA samples were investigated in our study. The samples

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include a stamp on a letter in a case of blackmail, a diaper, a slip wrapped in a plastic bag and a carpet in a case of sexual abuse, skeletal remains buried in the soil and paraffin-embedded cerebellar tissue of two murdered victims, a single telogen shed hair in a case of an assault of a supermarket and a cigarette butt from a bus stop in an identification case. 3. Results When designing a new multiplex system it is of utmost importance to establish a robust and reliable DNA typing system for all kinds of samples. The ShoP-PCR method was designed to make even amplification of highly degraded DNA possible. This multiplex approach includes the loci amelogenin, TH01, VWA, D3S1358, and D8S1179. None of the alleles described in the literature till date exceeds an allele length of more than 150 bp. Allele and size ranges of each locus are listed in Table 1. The amelogenin primers target a different region than the primer pair commonly used by the forensic community [24]. Our amelogenin primers are 1077 bp away from the region used in commercial kits and were originally described by [25]. As indicated in Table 1 this new target region exhibits a 3 bp difference between the X and Y alleles. PCR conditions and primer concentrations of our ShoP-PCR reaction mix were carefully adjusted to produce optimal results. Adjustment of ramping speeds was an important step, not only for the GeneAmp 2400 thermal cycler, but for other cyclers (GeneAmp 9600, Applied Biosystems, Darmstadt, Germany; PCR Express, Thermo Electron/Hybaid, Dreieich, Germany) either. To exclude mutations of primer binding sequences 200 healthy unrelated individuals were tested using our ShoP-PCR and the SGMplusTM Kit (Applied Biosystems, Darmstadt, Germany) or PowerPlex 16 SystemTM (Promega, Mannheim, Germany). Except in one case where allele 16 was not detectable in a 16/17 genotype of the VWA locus applying the SGMplusTM Kit, no differences were observed between the typing results of the

Table 2 Peak height of stutters in percentage (%) with S.E. (standard error) Allele (n)

6 7 8 9 9.3 10 11 12 13 14 15 16 17 18 19 20

TH01 (n = 44)

D8S1179 (n = 107)

D3S1358 (n = 123)

Stutter (%)

S.E. (%)

Stutter (%)

S.E. (%)

3.64 2.37 4.82 3.50 4.03 12.99

2.20 0.62 2.54 0.97 2.79

3.65 (4)

1.77

5.89 6.22 6.38 7.08 6.58 8.02 9.48

1.31 2.12 2.03 2.39 2.41 2.09 3.19

(10) (4) (8) (11) (10) (1)

(16) (8) (16) (33) (14) (13) (3)

VWA (n = 102)

Stutter (%)

S.E. (%)

Stutter (%)

S.E. (%)

7.69 8.89 9.56 10.30 11.16 9.77

2.03 2.42 2.60 2.71 2.53 0.44

2.46 6.08 6.53 7.15 8.67 10.46 7.40

1.25 2.73 1.80 2.05 2.90 2.00 0.14

(17) (35) (24) (24) (20) (3)

(11) (16) (22) (25) (17) (9) (2)

n is the number of observed and detectable allelic stutters; values in parentheses represent number of observations for each stutter product.

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Fig. 1. DNA typing results of the ShoP-PCR applying 100 pg (a), 25 pg (b), 12.5 pg (c) and 6.25 pg (d) of template DNA. Note allelic drop out in the panel at the bottom (d) for the loci amelogenin, TH01 and VWA, respectively.

commercially available kits or the ShoP-PCR. Frequencies of the 200 unrelated individuals were as expected according to the Hardy–Weinberg equilibrium. When applying 200 pg of DNA template, the four autosomal loci displayed differences of heterozygote imbalance. The lowest value was observed for the TH01 system with 4.07 11.30%, the highest value for D8S1179 with 13.38 13.29%. D3S1358 displays a heterozygote imbalance of 9.35 9.40%, VWA 7.23 10.64%.

The occurrence of allele-specific stutter bands is described in Table 2. Whereas peak height of stutters was similar for each allele independent of its size for the TH01 locus, peak height increases in dependence of size of the amplicons for the VWA and especially the D3S1358 loci, while D8S1179 displays no tendency. When a panel of different animal, bacterial and fungal DNA samples was applied, no signals were detected, except

Fig. 2. DNA as artificially degraded by digestion with DNase I for 2 min (a and d), 3 min (b and e) and 4 min (c and f). DNA profiles using the SGMplusTM Kit (A) and the ShoP-PCR (B). A complete profile of the five ShoP loci was obtained after 3 min and four of five loci were clearly visible after 4 min.


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Fig. 3. DNA tying result of the ShoP-PCR of DNA extracted from a slip (A) and a diaper (B) in a case of suspected sexual child abuse. Commercially available kits failed to display any signals.

Table 3 DNA typing results of eight different forensic materials Sample

Material

Age

ShoP

Commercial kits

1 2 3 4 5 6 7 8

Telogen shed hair Bone Slip Pampers Carpet Stamp Cigarette butt Paraffin-embedded tissue

2 years 7 years 2 years 7 days Unknown 6 months Unknown 15 years

5/5 3/5 5/5 5/5 5/5 4/5 5/5 4/5

0/5 0/5 1/5 0/5 0/5 0/5 2/5 2/5

orangutan and gorilla revealed some signals. Chimpanzee DNA displayed a profile with amelogenin, TH01, D3S1358 and VWA primers, albeit the specific signals for VWA were out of the range of the human ladder (data not shown). Different concentrations of template were tested and revealed a detection limit of 12.5 pg template DNA extracted from postmortem tissue without signs of decomposition. This equals the amount of roughly two diploid cells. When 6.25 pg were applied, allelic drop out occurs as expected (Fig. 1). Mixtures of 50 pg in a total of 1000 pg DNA (1:19) were clearly detectable (data not shown). When a DNase I test was performed, a complete DNA profile was obtained after a digestion of 3 min, whereas the SGMplusTM Kit displays only signals for the loci amelogenin, D3S1358 and D8S1179. At 4 min digestion four of five ShoP loci were clearly visible in contrast to the SGMplusTM Kit, where only locus D19S433 was detectable (Fig. 2A and B). As indicated in Table 3 our ShoP-PCR analysis revealed in forensic casework analysis for all eight samples a better result in comparison to the commercial kits. Examples of ShoP-PCR profiles are presented for a slip (Fig. 3A) and a diaper (Fig. 3B) in a case of sexual abuse. In five of the cases a complete DNA profile was detectable for the ShoP loci, in cases 6 and 8 four of the five loci were clearly visible. Even the sample of bone buried in the soil for 7 years displayed three complete loci. In comparison the SGMplusTM and/or the PowerPlex 16 SystemTM revealed less or even no results. 4. Discussion The short pentaplex PCR includes the loci amelogenin, TH01, VWA, D3S1358 and D8S1179. It was designed to allow successful DNA typing even in cases with highly degraded

DNA or a low amount of template. Because even poor quality DNA reveals fragment sizes of 100–150 bp [11,14,15], none of the common alleles of the five loci exceeds a fragment length of more than 150 bp. To avoid an overlap of alleles of two different loci labelled by the same fluorescent dye, primers were chosen with a 10 bp gap between the smallest common allele of one locus and largest of the other. Some samples revealed interfering peaks, which exhibit a broader appearance, easy to distinguish from specific dye-labelled PCR products. In other cases a few artificial peaks or dye blobs were detected, but artefact activity did not lead to difficulties in interpretation of results, because most of them were outside the fragment length of the true alleles of a locus or beneath the detection limit of 50 RFU. When designing primers for PCR amplification, sequence alignment procedures must exclude primer binding sites other than that of interest. Polymorphisms within primer binding regions may lead to the presence of a null allele [26]. This phenomenon could result in the occurrence of false homozygotes, as has been recently described for the D5S818 locus, where allele 10 segregates with a mutation of the primer binding site [27,28]. In PCRs with short target amplicons the closest position of primers to the STR of interest is not always that of choice, because flanking regions of primers often contain repeat structures or sequences, which could hamper the PCR by avoiding primer annealing or generating PCR artefacts [20]. So each of the designed PCRs should be carefully tested for artefacts and reliability in a large panel of human samples, animal DNA as well as forensic samples. Allelic drop out of the five loci was tested comparing the DNA profile of 200 individuals with results of the two commercially available kits PowerPlex 16 SystemTM (Promega, Madison, USA) and SGMplusTM Kit (Applied Biosystems, Darmstadt, Germany). In all cases identical profiles were obtained and no preferential amplification, allelic or loci drop out has been detected. The loss of allele 16 observed in the locus VWA applying the SGMplusTM Kit is supposed to be a result of a mutation in the primer binding site as had been already observed for allele 19 [29], because PowerPlex 16 SystemTM and ShoP-PCR profiles were identical. Specificity of the primers was tested applying a panel of animal, bacterial and fungal DNA. Only primate DNA revealed some detectable signals, partly off-ladder alleles, which has been already observed in other studies of human STR-loci, when primate DNA was tested [30,31].

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In dilution experiments at least 12.5 pg of human DNA produced reliable results, albeit heterozygosity imbalance was observed in some cases. It is well known that under conditions when only a small amount of DNA is available, a tendency for preferential amplifications occurs [32] and allelic imbalance and allelic drop out should be kept in mind. The short fragments of the ShoP-PCR increase sensitivity due to a higher amplification efficiency and a complete profile was detectable even when amounts of 12.5 pg were applied (Fig. 1). When 6.25 pg template DNA were subjected to PCR, allelic drop out was observed, because stochastic effects of primer annealing and PCR amplification are expected. In other multiplex PCRs these phenomena are observed when applying DNA amounts of 200 pg [33]. Another important issue to address in validation procedures is the reliability and sensitivity when mixed stains are analysed, because the limit of detection of the minor component in mixed DNA extracts depends on the amount of this component. Using a total of 1000 pg template, it was possible to obtain a complete profile of an amount of 50 pg DNA. The detectable limit of 1:19 of the minor component is similar to other multiplex approaches [33,34]. The major advantage of our system becomes quite clear, when degraded material has been analysed. Degraded DNA was prepared by DNase I digestion under controlled conditions. Even after digestion of 4 min four of five loci were clearly visible. It is not surprising that allelic drop out of the largest locus, D3S1358 occurs at first. Failure of signal detection for the locus FGA was observed in a similar manner when the AmpFISTRTM Blue PCR Amplification Kit was applied and two of three loci were detectable [34]. Our approach allows typing of degraded DNA due to the small size of the target fragments, because none of the detectable alleles exceeds 150 bp in length. A disadvantage of our ShoP-PCR is the relatively low power of discrimination with 1:3.16 104, because only four autosomal loci are displayed. In comparison, the Power of discrimination for the SGMplusTM Kit (1:3.3 1012) and the PowerPlex 16 System (1:1.83 1017) are orders of magnitude higher. So performance of commercial kits is better in cases when amount of intact DNA is sufficient. Because the aim of our study was to present a PCR useful for degraded material in forensic casework analysis, the ShoP-PCR was tested on a panel of forensic samples like telogen shed hair, bone buried in the soil or formalin-embedded tissues, which revealed only up to two loci, when SGMplusTM Kit or PowerPlex 16 SystemTM were applied. Telogen shed hairs are often found at crime scenes. Due to its nature, DNA enclosed in the keratin matrix is intensively degraded and typing of shed hairs without a bulb often reveals no results [5]. As indicated in Table 3 a single telogen shed hair collected from the clothes of a victim displayed the complete profile. DNA extracted from human bones buried in the soil or found in damp environment is often extensively degraded [13,16]. When typing DNA extracts of bones of air crash victims it was observed, that allelic or loci drop out occurs, when alleles were longer than 200 bp [35]. As has been shown for bone buried in the soil (case 2), our ShoPPCR approach will lead to successful results, due to the small

size of target fragments. Formalin-fixation induces degradation of DNA, even after fixation times of 3 h [36,37]. In routine pathology tissue is often fixed for at least 2 days in buffered or unbuffered formalin before paraffin embedding. Applying formalin-fixed, paraffin-embedded tissue (case 8) after a storage time of 15 years a complete DNA profile was obtained, so this PCR will be useful when only paraffin-embedded material is available, which is often stored over decades of time. 5. Conclusion In cases with an amount of DNA of more than 12.5 pg or in cases when only highly degraded DNA is available our system allows successful DNA typing. The ShoP-PCR approach seems to be extremely useful in typing of telogen hairs, highly putrefied tissue or tissue fixed in formalin for longer periods of time. The design of new mini primer pairs and their combination in multiplex PCRs provide improved results when allelic drop out occurs due to degraded DNA or due to mutations of primer binding sites. In future, it will be important to have more than a handful of different multiplex mini-STRs to ensure optimal results in forensic casework analysis. References [1] P. Hoff-Olsen, S. Jacobsen, B. Mevag, B. Olaisen, Microsatellite stability in human post-mortem tissues, Forensic Sci. Int. 119 (2001) 273–278. [2] C. Kimpton, D. Fisher, S. Watson, M. Adams, A. Urquhart, J. Lygo, P. Gill, Evaluation of an automated DNA profiling system employing multiplex amplification of four tetrameric STR loci, Int. J. Legal Med. 106 (1994) 302–311. [3] R. Schoske, P.M. Vallone, C.M. Ruitberg, J.M. Butler, Multiplex PCR design strategy used for the simultaneous amplification of 10 Y chromosome short tandem repeat (STR) loci, Anal. Bioanal. Chem. 375 (2003) 333–343. [4] J.M. Butler, J.M. Devaney, M.A. Marino, P.M. Vallone, Quality control of PCR primers used in multiplex STR amplification reactions, Forensic Sci. Int. 119 (2001) 87–96. [5] A. Hellmann, U. Rohleder, H. Schmitter, M. Wittig, STR typing of human telogen hairs—a new approach, Int. J. Legal Med. 114 (2001) 269–273. [6] A. Alvarez Garcia, I. Munoz, C. Pestoni, M.V. Lareu, M.S. RodriguezCalvo, A. Carracedo, Effect of environmental factors on PCR-DNA analysis from dental pulp, Int. J. Legal Med. 109 (1996) 125–129. [7] J. Burger, S. Hummel, B. Hermann, W. Henke, DNA preservation: a microsatellite-DNA study on ancient skeletal remains, Electrophoresis 20 (1999) 1722–1728. [8] M.M. Holland, D.L. Fisher, L.G. Mitchell, W.C. Rodriquez, J.J. Canik, C.R. Merril, V.W. Weedn, Mitochondrial DNA sequence analysis of human skeletal remains: identification of remains from the Vietnam War, J. Forensic Sci. 38 (1993) 542–553. [9] P. Hoff-Olsen, B. Mevag, E. Staalstrom, B. Hovde, T. Egeland, B. Olaisen, Extraction of DNA from decomposed human tissue. An evaluation of five extraction methods for short tandem repeat typing, Forensic Sci. Int. 105 (1999) 171–183. [10] S. Banaschak, A. Du Chesne, B. Brinkmann, Multiple interchanging of tissue samples in cases of breast cancer, Forensic Sci. Int. 113 (2000) 3–7. [11] M. Ho¨ss, P. Jaruga, T.H. Zastawny, M. Dizdaroglu, S. Paabo, DNA damage and DNA sequence retrieval from ancient tissues, Nucl. Acids Res. (7) (1996) 1304–1307. [12] K. Bender, M.J. Farfan, P.M. Schneider, Preparation of degraded human DNA under controlled conditions, Forensic Sci. Int. 139 (2004) 135–140.

C. Meissner et al. / Forensic Science International 166 (2007) 121–127 [13] M. Graw, H.J. Weisser, S. Lutz, DNA typing of human remains found in damp environments, Forensic Sci. Int. 113 (2000) 91–95. [14] S. Paä¨bo, Ancient DNA: extraction, characterization, molecular cloning, and enzymatic amplification, Proc. Natl. Acad. Sci. U.S.A. 86 (1989) 1939–1943. [15] O. Handt, M. Krings, R.H. Ward, S. Paä¨bo, The retrieval of ancient human DNA sequences, Am. J. Hum. Genet. 59 (1996) 368–376. [16] D.L. Fisher, M.M. Holland, L. Mitchell, P.S. Sledzik, A.W. Wilcox, M. Wadhams, V.W. Weedn, Extraction, evaluation, and amplification of DNA from decalcified and undecalcified United States Civil War bone, J. Forensic Sci. 38 (1993) 60–68. [17] C. Lassen, S. Hummel, B. Herrmann, Comparison of DNA extraction and amplification from ancient human bone and mummified soft tissue, Int. J. Legal Med. 107 (1994) 152–155. [18] G.G. Shutler, P. Gagnon, G. Verret, H. Kalyn, S. Korkosh, E. Johnston, J. Halverson, Removal of a PCR inhibitor and resolution of DNA STR types in mixed human-canine stains from a five year old case, J. Forensic Sci. 44 (1999) 623–626. [19] M. Strom, S. Rechitsky, Use of nested PCR to identify charred human remains and minute amounts of blood, J. Forensic Sci. 43 (1998) 696–700. [20] J.M. Butler, Y. Shen, B.R. McCord, The development of reduced size STR amplicons as tools for analysis of degraded DNA, J. Forensic Sci. 48 (2003) 1054–1064. [21] P. Wiegand, M. Kleiber, Less is more—length reduction of STR amplicons using redesigned primers, Int. J. Legal Med. 114 (2001) 285–287. [22] S. Rozen, H. Skaletsky, Primer3 on the WWW for general users and for biologist programmers, Meth. Mol. Biol. 132 (2000) 365–386. [23] P.S. Walsh, D.A. Metzger, R. Higuchi, Chelex 100 as a medium for simple extraction of DNA for PCR-based typing from forensic material, Biotechniques 10 (1991) 506–513. [24] K.M. Sullivan, A. Mannucci, C.P. Kimpton, P. Gill, A rapid and quantitative DNA sex test: fluorescence-based PCR analysis of X–Y homologous gene amelogenin, Biotechniques 15 (1993) 636–638, 640–641. [25] H. Haas-Rochholz, G. Weiler, Additional primer sets for an amelogenin gene PCR-based DNA-sex test, Int. J. Legal Med. 110 (1997) 312–315.

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LoComatioN: A software tool for the analysis of low copy number DNA profiles Peter Gill a,*, Amanda Kirkham a, James Curran b b

a Forensic Science Service, Trident Court, 2960 Solihull Parkway, Solihull B37 7YN, UK Department of Statistics, The University of Auckland, Private Bag 92019, Auckland, New Zealand

Received 23 February 2006; accepted 11 April 2006 Available online 8 June 2006

Abstract Previously, the interpretation of low copy number (LCN) STR profiles has been carried out using the biological or ‘consensus’ method— essentially, alleles are not reported, unless duplicated in separate PCR analyses [P. Gill, J. Whitaker, C. Flaxman, N. Brown, J. Buckleton, An investigation of the rigor of interpretation rules for STRs derived from less than 100 pg of DNA, Forens. Sci. Int. 112 (2000) 17–40]. The method is now widely used throughout Europe. Although a probabilistic theory was simultaneously introduced, its time-consuming complexity meant that it could not be easily applied in practice. The ‘consensus’ method is not as efficient as the probabilistic approach, as the former wastes information in DNA profiles. However, the theory was subsequently extended to allow for DNA mixtures and population substructure in a programmed solution by Curran et al. [J.M. Curran, P. Gill, M.R. Bill, Interpretation of repeat measurement DNA evidence allowing for multiple contributors and population substructure, Forens. Sci. Int. 148 (2005) 47–53]. In this paper, we describe an expert interpretation system (LoComatioN) which removes this computational burden, and enables application of the full probabilistic method. This is the first expert system that can be used to rapidly evaluate numerous alternative explanations in a likelihood ratio approach, greatly facilitating court evaluation of the evidence. This would not be possible with manual calculation. Finally, the Gill et al. and Curran et al. papers both rely on the ability of the user to specify two quantities: the probability of allelic drop-out, and the probability of allelic contamination (‘‘drop-in’’). In this paper, we offer some guidelines on how these quantities may be specified. # 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Low copy number (LCN); Automation; LoComatioN; Likelihood ratio; Propositions

1. Introduction Low copy number (LCN) DNA profiling is a term used to describe the analysis of very small amounts of DNA from a few cells (200 pg) of DNA present. The assumption that the peak height/area of alleles is proportional to the actual amount of DNA present [5–7] is well established, however with LCN, stochastic effects compromise this [8].

P. Gill et al. / Forensic Science International 166 (2007) 128–138

Although a probabilistic method has been published [9,10] the likelihood ratio (LR) calculations are far too complex to carry out manually, especially when the theory was extended to include mixture interpretation with multiple contributors. An interim method, called the ‘‘biological model’’, was introduced. The biological model depended upon the derivation of a ‘‘consensus’’ profile. A consensus profile only reports alleles that were reproducible from two or more replicate analyses of an extracted DNA sample [9,11]. As contamination tended to be a single tube event of low probability, it was unlikely that these alleles would be replicated in different analyses and reported in the consensus profile. The biological model tended to behave in a conservative way relative to the formal statistical model, but does not make full use of the information available in the replicate DNA profiles. Curran et al. [12] recently introduced a set theoretic formalization to allow the automatic calculation of LRs for LCN profiles. This method has been implemented in a fully functional software application called LoComatioN. LoComatioN is a hypothesis driven expert system that enables LRs for any number of different LCN propositions to be evaluated. The construction of the LR follows the standard format, requiring an evaluation of the probability of observing the evidence under the prosecution and the defence hypotheses, Hp and Hd, respectively. We call these hypotheses ‘‘propositions’’. An example might be a rape case where a woman alleges she was raped by exactly one man. The prosecution proposition (Hp) is that the crime scene stain consists of the victim (V) and the suspect (S). The alternative or defence proposition (Hd) is that the victim and someone unrelated to the suspect were the only contributors. We denote this V + unknown (U). Of course, more complex propositions may be suggested by the defence, and it may be desirable to evaluate the LR with respect to several different pairs of propositions. Although the theory to analyse different propositions exists, in practice the computational requirements for a reporting officer doing the calculations manually are very time-consuming (and therefore potentially error prone). As a result this option is often precluded. This inability to provide adequate calculations to the court for multiple propositions is a limiting factor and might be detrimental because cases may be reported as ‘‘inconclusive’’. The advantage of LoComatioN, is that the scientist is able to input data from up to five replicate analyses, and is able to consider up to five contributors to any mixture where the propositions can be altered at will. This means that for virtually all mixtures, the scientist can now rapidly evaluate any number of propositions that the court requires. We hope that this means the ‘‘inconclusive’’ category will become something of the past. The ability to evaluate multiple propositions means that LoComatioN has an important role as an exploratory tool. We show how sensitive the LR is to different conditioning statements/propositions by reference to a complex case. To facilitate the court going process and to resolve potential uncertainties about the effects of different conditioning statements, we have introduced guidance to formulate propositions by incorporating some generalisations of Brenner et al. [13], Weir [14] and Buckleton et al. [15].

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2. Formulation of propositions We use the following notation to show the respective propositions in a typical mixture case conditioned on a victim (V), suspect (S) and unknown (U) where the propositions are Hp: V + S and Hd: V + U: LR ¼

PrðEjHp Þ PrðEjHd Þ

where the likelihood ratio is comprised of Hp (the prosecution proposition) in the numerator and Hd (the defence proposition) in the denominator. E is the evidence of the DNA crime profile. The prosecution proposition (Hp) is initially based upon the testimony of witnesses and other circumstances of the case. DNA profiling is carried out on a crime stain and the results are used to confirm or to refute the proposition. If the profile matches the suspect (S), then the proposition Hp is supported. In a DNA mixture, alleles that match S may be present, providing support for Hp. However, additional alleles from other sources may also be present and these may provide support for the alternative defence proposition (Hd). Further refinement of propositions might be required [16,17]. It is not always easy to specify propositions in complex cases where multiple perpetrators/victims may be present. The DNA result itself may indicate that different explanations are possible. Furthermore, it is possible that Hp and Hd could be very different from each other. For example under Hp we might consider a victim and suspect to be the contributors (V + S), whereas under Hd we might examine more complex propositions such as three unknowns being the contributors to the stain (U1 + U2 + U3). There is a common misconception that the number of contributors (nc) under Hp and Hd should be the same. They do not. 3. Allele drop-out and the Q designation Drop-out is an important defining feature of LCN. There are two aspects to be included in probabilistic calculations: the first is to estimate the probability of drop-out Pr(D) and the second is to include the dropped out allele in the probabilistic assessment. Originally the F designation [9] was used to signify the possibility of drop-out event; a sample that shows a single allele, a, can be designated aF, where F can be any allele, including a. The probability of F = 1 since it includes all allelic possibilities, the probability of a is pa, hence Pr(aF) = 2pa. However, this formula may not be conservative, i.e. can over estimate the LR in favour of Hp [9]. This is more likely to happen when the probability of drop-out is low. We have introduced an improved concept into LoComatioN to facilitate programming. If drop-out is required to support a proposition we consider that the identity of the unknown allele Q can be anything, except those already observed in the DNA profile: PrðQÞ ¼ 1

n X i¼1

pi

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where n alleles are observed in the profile and pi is the frequency of the ith allele. Consider the following simple example. The crime stain profile at locus THO1 has one allele of type 11. The suspect (S) is genotype 9,11. Under Hp, we argue that allele 9 must have dropped out. Under Hd, evaluation of the alternative explanation (U) would include a probabilistic determination of all possible pairwise combinations (that must include allele 11): 4,11; 5,11; 6,11, etc. a total of nine different combinations to be computed. The Q designation is used, given drop-out, where Pr(Q)=pQ = 1 p11, and this achieves exactly the same result in just one computational step. The combination p211 is included under the hypothesis that no drop-out has occurred. When mixtures are considered, the computational savings are even greater. 3.1. Using the Q designation to formulate Hp and Hd As an example, if the stain profile E = abc; S = ab; nc = 2 and all three alleles are low level, then under Hp, if drop-out has occurred we consider all pairwise combinations of cQ where p Q = 1 p a p b p c: PrðEjHp ; DÞ ¼ PrðEjHp ; DÞPrðDÞ;

Alternatively, if no drop-out has occurred: ¯ ¼ PrðEjHp ÞPrðDÞ; ¯ PrðEjHp ; DÞ PrðEjHp Þ ¼ p2c þ 2 pa pc þ 2 pb pc

(2)

Hence, Pr(EjHp) comprises the sum of terms (1) and (2). Under Hd, with two unknown (U1, U2) contributors, given drop-out: PrðEjHd Þ ¼ 24 pa pb pc pQ (3)

With no drop-out, such that alleles a, b, c are shared between two contributors: ¯ ¼ PrðEjHd ÞPrðDÞ; ¯ PrðEjHd ; DÞ PrðEjHd Þ ¼ 12 pa pb pc ð pa þ pb þ pc Þ

(4)

The likelihood ratio is LR = Pr(EjHp)/Pr(EjHd): LR ¼

A contaminant event is the spurious occurrence of single alleles from multiple sources, assumed to be independent events. Probability of contamination is estimated from negative controls as described by Gill and Kirkham [4]. Laboratory records d ¼ 0:05 per sample where indicate a level of approximately PrðCÞ d ¼ n PrðCÞ LN where n is the number of alleles observed in a series of negative controls and N the total number of negative controls analysed and L is the number of loci tested per sample (whether or not alleles are actually observed). The ‘‘hat’’ over Pr(C) indicates that this is an estimate. The probability of any given allele appearing as a contaminant is approximated to be the same as the probability of its occurrence in the white Caucasian population (from a frequency database). 6. A fully worked example with drop-out and contamination

PrðEjHp Þ ¼ 2 pc pQ (1)

PrðEjHd ; DÞ ¼ PrðEjHd ÞPrðDÞ;

5. Estimation of Pr(C)

¯ PrðDÞð2 pa þ 2 pb þ pc Þ þ PrðDÞð2 pQ Þ ¯ pa þ pb þ pc Þ þ PrðDÞð2 pQ Þ 12 pa pb ½PrðDÞð

(5)

A suspect’s genotype at a particular locus is ab. The crime sample profile (E) is a. The prosecution proposition (Hp) states that the suspect (S) is the offender. This can only be explained if drop-out of allele b had occurred. The defence proposition (Hd) is that the offence has been committed by an unknown individual (U), unrelated to the suspect. Using our previously defined notation the likelihood ratio using propositions Hp: S and Hd: U is LR ¼


Formulae for the numerator and denominator are given in Table 1, illustrating use of the Q virtual allele designation in conjunction with the probability of drop-out, Pr(D) and the ¯ ¼ 1 PrðCÞ. probability of no contamination PrðCÞ The calculations for this simple example are just about manageable by hand, but most propositions will be much more complicated than this, comprising mixtures from two or more people and two or more replicates. An example of LoComatioN output and associated statistical analysis is given in Appendix II. 7. Casework example to illustrate evaluation of multiple propositions

4. Estimation of Pr(D)

7.1. Case circumstances

From Gill et al. [8], for low copy number DNA, in the absence of degradation, it is reasonable to assume that the chance of allele drop-out is independent of the locus. Note that if significant degradation has occurred then high molecular weight loci will be affected preferentially. Under LCN conditions, where DNA is amplified 34 cycles, the biochemistry/detection system will distinguish a single copy of DNA at any SGM+ locus [1]. We provide a method to estimate Pr(D) by simulation based on the assumption that Pr(D) is constant across all loci (Appendix I).

Late one night, two cohabiting females were woken by a masked man who had broken into their flat. The intruder threatened the women with a hammer. He ordered them to engage in sexual acts but the victims did not comply. One shouted for help and the other fought off the assailant. Both victims sustained injuries caused by the hammer. The assailant ran away, discarding the hammer outside the flat, which was subsequently recovered. On questioning, the suspect denied that the hammer was his.


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Table 1 An illustration of the correct use of Q when drop-out is considered Suspect (Mj)

Pr(Mj)

Pr(E = ajMj)

Product

Hp numerator calculation a,b

1

¯ ¯ PrðDÞPrðDÞPrð CÞ

¯ ¯ PrðDÞPrðDÞPrð CÞ

Possible random men (Mj)

Pr(Mj)

Pr(E = ajMj)

Producta

Hd denominator calculation a,a a,Q Q,Q

p2a 2papQ p2Q

¯ ¯ 2 PrðCÞ PrðDÞ ¯ ¯ PrðDÞPrðDÞPrðCÞ Pr(D)2Pr(C)pa

¯ p2a ¯ 2 PrðCÞ PrðDÞ ¯ pa pQ ¯ 2PrðDÞPrðDÞPrð CÞ 2 PrðDÞ PrðCÞ pa p2Q

The crime stain is of type a, the suspect is genotype ab and under Hp, we assume that given S, allele b has dropped out with probability Pr(D). Under Hd, given that the suspect is innocent, then drop-out may or may not have happened. We evaluate a set of possible ‘‘random man’’ genotypes worth considering M1, M2, M3. a Denominator = sum of the products.

Table 2 Tabulated PCR amplification results from casework example Allelic results observed at each loci tested Amelo D3 Sample (R1) Sample (R2) Victim 1 Victim 2 Suspect

VWA

D16

D2

D8

D21

D18

11 13 14 20 23 24 25 11 12 13 15 28 31

D19

THO

FGA

12 14 15.2 17.2

6 8 9 9.3 22

XY

14 16 15 16 19

XY

14 16 15 16 17 19 11 13 14 20 24 25

11 12 13 15 28 29 30 31 31.2 13 14 16 17 12 13 14 15.2 17.2 6 8 9 9.3 22 23 25

XX XX XY

16 16 15 16 15 17 16 19 14 16 15 19

11 15 11 13 12 13

13 13 12 13 11 14

20 20 18 25 24 25

29 30 29 30 28 31

17 17 15 17 14 17

12 14 14 14 15.2 17.2

68 67 9 9.3

22 25 20 22 22 23

7.2. Propositions and DNA analysis

7.3. Traditional consensus method (biological model)

The overall purpose of the investigation was to establish whether the hammer was relevant evidence—i.e. was the hammer used/not used in the attack? The specific purpose of the DNA investigation was to establish if there was evidence to support or to refute alternative propositions [16] of the kind:

The consensus approach [9] was dependent upon experimental reproducibility of individual alleles. The method compared two separate PCR amplification results and the calculation of the LR was derived from the consensus of duplicated alleles at each locus in R1 and R2 (Table 3). The consensus approach uses the F designation to signify drop-out. The assumptions in this model were:

Hp: the DNA from the hammer originated from the suspect and two victims; Hd: the DNA from the hammer originated from an unknown individual unrelated to the suspect, and two victims. The hammer-head was swabbed and two LCN PCR amplification replicates (R1 and R2) were obtained (Table 2). The results showed that at some loci more than two alleles were present, suggesting a mixture (following guidelines of Clayton et al. [6]). Both PCR amplification and extraction reagent negatives were blank, indicating no obvious source of gross contamination. From laboratory records of negative controls, Pr(C) = 0.05.

1. a three person mixture, nc = 3; 2. both victims were considered to be contributors under both Hp and Hd. We evaluate propositions Hp: V1 + V2 + S and Hd: V1 + V2 + U. The standard approach was used: any alleles that matched either of the victims were subtracted to leave a partial profile (Table 4), interpreted as S under Hp and U under Hd. There were seven alleles shared between both victims and the suspect. The F designation was subsequently assigned to

Table 3 Tabulated consensus PCR amplification results from R1 and R2 in the casework example Allelic results (consensus) observed at each loci tested

Consensus result

Amelo

D3

VWA

D16

D2

D8

D21

XY

14 16

15 16 19

11 13 14

20 24 25

11 12 13 15

28 31

NB. The alleles in bold denote alleles that could be attributed to the victims.

D18

D19

THO

FGA

12 14 15.2 17.2

6 8 9 9.3

22

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Table 4 Tabulated ‘foreign’ alleles defining the assailant’s DNA components in the DNA mixture taken from the hammer ‘Foreign’ alleles defining the offender’s DNA profile

Offender

Amelo

D3

VWA

D16

D2

D8

D21

D18

D19

THO

FGA

Y

14 F

FF

11 14

24 F

12 F

28 31

FF

15.2 17.2

9 9.3

FF

any locus where one allele was present [9] to signify the possibility of allele drop-out: LR ¼


¼ 1:55 106 ðwhite Caucasian reference databaseÞ 7.3.1. LoComatioN analysis We now evaluate the effect of comparing different alternative pairs of propositions in the context of the fully probabilistic model that incorporates probabilities of drop-out and contamination into the LR [9,12]. This model is much more powerful than the consensus approach, taking the interpretation process a stage further. A consensus profile is not derived. Consequently, it is possible to calculate the LR relative to a single analysis (R1), although replicate (R1, R2, . . ., Rn) analyses are much to be preferred, because more information is incorporated into the calculation. The Q virtual allele is used when drop-out occurs, instead of F in the ‘consensus’ method. 7.4. Application of the theory to evaluate multiple propositions Casework circumstances are often complex. Multiple pairs of propositions may be possible, but the prime consideration is that the suspect S is always in the numerator under Hp and this is replaced by U in the denominator under Hd. A dialogue may ensue in court where the scientist is requested to evaluate the LR using multiple ‘what-if’ propositions. LoComatioN can be used as an exploratory tool for this purpose. The profile in the example can be interpreted using several different propositions conditioned on nc = 2 persons or alternatively nc = 3 persons mixtures, from an average of 32 bands in R1 and R2 DNA profiles (Table 2). The estimated upper d bound on the value of the probability of drop-out is, PrðDÞ 0:95 ¼ 0:16 and 0.38, respectively (Appendix I). From a preliminary assessment of evidence in this case, the first iteration of propositions is as follows. Proposition 1. Hp: V1 + V2 + S and Hd: V1 + V2 + U. However, examination of the DNA results suggested a possible alternative explanation. All of the alleles that could be attributed to victim two are shared with either victim one or the suspect. Therefore, the propositions could be modified as follows. Proposition 2. Hp: V1 + S and Hd: V1 + U. Now we condition upon a two person mixture. However, this would require five alleles to be explained as

contamination events (D18-16, D21-31.2, D2-23, D16-12, VWA-17). As Pr(C) = 0.05 per DNA profile, this would be unlikely. A more plausible explanation would be that DNA from three contributors was present, where one was unknown under Hp and Hd (i.e. transfer of DNA to the hammer from an unknown person could have occurred before the crime event). The absence of a DNA profile from V2 does not imply that she was not hit with the hammer, since transfer of DNA as a result of physical contact is dependent upon unquantifiable factors and is not a foregone conclusion [18]. Proposition 3. Hp: V1 + S + U and Hd: V1 + U1 + U2. For illustrative purposes only we also consider two separate, albeit highly improbable, propositions (since we believe that V2 DNA is absent), but it is interesting to determine the effect on the LR if V2 is substituted for V1. Proposition 4. Hp: V2 + S and Hd: V2 + U. Proposition 5. Hp: V2 + S + U1 and Hd: V2 + U1 + U2. Finally, to illustrate an unbalanced pair of propositions where Hp is anchored on V1 and S we evaluate Hd using V1 + U1 + U2—since nc is different under Hp and Hd, Pr(D) is conditioned on nc = 2 and 3, respectively. Proposition 6. Hp: V1 + S1 and Hd: V1 + U1 + U2. The probability of contamination was kept constant (Pr(C) = 0.05) for all propositions; with Pr(D) varied from 0.01 to 0.95 by 0.05 increments. LRs were calculated across all loci for each level of Pr(D) (Fig. 1). The highest LRs were calculated using Proposition 6 Hp: V + S and Hd: V1 + U1 + U2, followed by Proposition 2 Hp: V1 + S and Hd: V1 + U. However, we restate that neither is optimal for court reporting for the reasons outlined previously. Whereas the proposition V1 + S appeared to favour Hp the most, given the large number of unknown alleles that cannot be realistically explained by contamination, we advocate Hp: V1 + S + U as the simplest and most realistic prosecution proposition. Proposition 1: Hp: V1 + V2 + S and Hd: V1 + V2 + U and Proposition 3: V1 + S + U2 and Hd: V1 + U1 + U2 give LRs that are very similar. The substitution of V2 with U2 makes very little difference to the result, i.e. it does not assist the defence to argue whether V2 is present or whether an unknown person was present in the crime profile. The lowest LRs were calculated with Proposition 4: Hp: V2 + S and Hd: V2 + U. This result was not unexpected, as seven (out of twenty) of the alleles of victim two were not reproduced in any of the amplification replicate results—giving a much smaller numerator value.


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Fig. 1. Casework example, log10 genotype likelihood ratios vs. probability of drop-out for each pair of propositions tested. The large striped arrows correspond d d to the x-axis estimate of probability of drop-out PrðDÞ 0:95 for nc = 2 and the large solid arrows estimate probability of drop-out PrðDÞ0:95 for nc = 3 (32 allele profile). A horizontal line to the y-axis gives an estimate of the log10 LR. For each line on the graph, the alternative prosecution and defence propositions are given in the format Hp/Hd.

Finally, Proposition 6: Hp: V1 + S and Hd: V1 + U1 + U2 gave the greatest LR, but as previously indicated; invoking multiple independent contaminant alleles is not particularly realistic and was therefore not advocated. Proposition 3 was preferred, whilst noting that Proposition 1 made very little difference with respect to the final LR at the predicted drop-out level Pr(D) = 0.38. The main purpose of this demonstration was to show how easy it is to rapidly evaluate any propositions required by the court. An important feature is that all calculations are relatively insensitive to Pr(D) since the fall in LR was small over the realistic range of Pr(D). 7.5. Comparison with the consensus model The consensus, or biological model results, evaluated Hp: V1 + V2 + S and Hd: V1 + V2 + U and the LR = Pr(EjHp)/ Pr(EjHd) = 1.55 106. This was conservative relative to all propositions tested except for the unrealistic pair of Propositions 4: Hp: V2 + S and Hd: V2 + U.

8. Discussion Whereas the contamination parameter is relatively straightforward to estimate from experimental observation of negative controls [4], the drop-out parameter is more problematic. Under the assumption that allelic drop-out is random [8] we currently estimate the distribution of this parameter from the number of alleles present in the DNA profile, relative to profiles randomly generated from a reference population database such as Caucasian. Different distributions result from different population databases—but the differences are minor (data not shown). It is currently impracticable to estimate multiple drop-out parameters (one for each potential contributor), consequently we effectively use an average (unweighted) value. It is informative to evaluate the effect of altering the drop-out parameter of individual loci comparing Hp: S + U and Hd: U1 + U2 (Table 5). Under Hp, S = ab and U = cd. To simplify calculations we evaluate a locus where alleles are either common ( p = 0.1) or rare ( p = 0.02). We have not considered

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Table 5 LRs calculated for typical drop-out and contamination events at a single locus where Pr(allele) = 0.1 or 0.02, respectively, evaluating Hp: S + U and Hd: U1 + U2 Condition

No drop-out; no contamination 1 suspect allele dropped out 1 unknown allele dropped out Both suspect alleles dropped out 1 contamination event; no drop-out 1 contamination event; 1 suspect allele dropped out

Match probability of allele = 0.1

Match probability of allele = 0.02

Pr(D) = 0.1

Pr(D) = 0.5

Pr(D) = 0.9

Pr(D) = 0.1

Pr(D) = 0.5

Pr(D) = 0.9

8.3 0.4 9.1 0.21 5 0.03

8.3 0.98 2.5 0.21 5 0.24

8.3 1.16 0.3 0.21 5 1.3

208 3.44 77.5 0.17 125 0.14

208 4.3 10.7 0.17 125 1.2

208 4.42 1.2 0.17 125 6.7

the effect of F ST in these comparisons. Nevertheless, we illustrate that the following generalisations are useful when evaluating any locus: (a) If it is not necessary to invoke drop-out or contamination under Hp in order to explain S then the LR is constant because Pr(D) cancels out in the numerator and denominator. (b) If one S allele has dropped out then the evidence tends to be neutral, or favours Hd, dependent upon whether the remaining S allele is rare. (c) If both S alleles have dropped out, i.e. complete locus dropout under Hp then the evidence always favours Hd independent of Pr(D). (d) Similarly, Pr(D) cancels when a contamination event occurs provided both suspect alleles are present—the profile is type abcde. Hp is favoured. (e) If one contaminant band and one drop-out event has occurred under Hp, then the LR will favour Hd; the greater Pr(D), the greater the LR becomes. (f) Conversely, if an unknown allele is alleged to have dropped out under Hd, then this also reduces the LR—the greater Pr(D), the lower the LR becomes. The biggest effect occurs when Hp can only be explained if drop-out has occurred (e.g. the profile is abd) regardless of the value of Pr(D) chosen within the range 0.1 < Pr(D) < 0.9, the LR drops by an approximate order of magnitude within this range. In addition, the lower the Pr(D) the less likely it is that drop-out is a satisfactory explanation under Hp, and consequently the lower the LR becomes.

under Hd was of trivial consequence. This leads us to propose a possible new approach to assist in the evaluation of evidence. Reasonable (multiple) pairs of propositions can be selected in agreement with the court requirements. A minimum LRmin (the lowest LR calculated) can provide a base-line. It is worth noting that all propositions will have S in the numerator substituted by U in the denominator, i.e. we have shown that any differences between LRs are a result of secondary issues that relate to the number and conditioning of contributors to the crime stain evidence. If LR differences are trivial or bounded by LRmin, then the court may view that the peripheral issues are simply not relevant to the evidence, as it does not affect the primary consideration of whether the suspect contributed to the crime stain. If there are several alleles from an unknown source in a crime sample, then it is unlikely that these are explained by a contamination probability which is strictly only valid under the assumption that the contaminant alleles present are independent, and not from a single source. With Pr(C) = 0.05, on average, we would expect only one to two contaminant alleles. Consequently we recommend that profiles with three or more alleles that cannot be explained by the casework circumstances are always evaluated by invoking an addition unknown (U) contributor as the most reasonable explanation. The second recommendation is to use the Q designation with caution under Hp, since it always increases Pr(EjHp). Conversely, to maximise Pr(EjHd) it is reasonable to use Q if the alleles are at low level. 8.2. LoComatioN as a LR calculator for ‘conventional’ DNA profiles

8.1. General conclusions on forming propositions LoComatioN enables rapid evaluation of multiple propositions. Sometimes it is difficult to formulate propositions in casework because of uncertainties surrounding the casework circumstances. This is especially true for DNA profiles where the amount of DNA is limited. In addition, there may be ample opportunity for transfer of DNA to have occurred before the crime event. The case example described provided an opportunity to evaluate the effect of choosing different propositions for analysis. The profile was a mixture where it was unclear whether a victim’s DNA was present. We showed that the issue of whether V2 or U was the best explanation

LoComatioN can also be used to calculate LRs from conventional 28 cycle DNA profiles as well. There is a misconception that the low copy number definition applies only to elevated PCR cycle number. However, the defining feature of LCN is drop-out and drop-in. These phenomena also occur with 28 PCR cycles. Most laboratories have guidelines to indicate whether a given profile is sufficient for conventional interpretation (i.e. precluding allele drop-out). Many will report major/minor mixtures where the minor component is attributed to the suspect under Hp, but allele drop-out may be observed. All of the considerations described previously, also apply to low level DNA analysed using 28 PCR cycles.


If the alleles at a locus are above an experimentally defined threshold level (e.g. 150rfu) then allele drop-out is unlikely to occur. Under these conditions, Pr(D) 0 and consequently the Q designation is not relevant to the calculation of the LR. Under these conditions the theory used by LoComatioN converges to models previously described [19]—however, the advantage is that Pr(C) can be incorporated, multiple propositions can be evaluated, and furthermore the information from several replicates can be combined into one LR if necessary. Appendix A A.1. Simulation of the empirical likelihood for the probability of drop-out In the following simulations we consider the number of contributors, nc, and the probability of contamination Pr(C) to be fixed in advance. The goal of the simulations is to estimate the probability of observing x alleles at L loci given that the probability of drop-out is equal to D, Pr(D) = D. That is, we wish to estimate Pr(xjD, C, nc). Given that Pr(C) and nc are constant, this becomes Pr(xjD). The problem is that we do not know D. Therefore we use the data, x, to estimate D using maximum likelihood estimation. This quantity is called the likelihood of D and is denoted L(D). However, we do not know the likelihood function of D given x either, so we have constructed a simulation in order to estimate the likelihood function of D given x. As L(D) is estimated from simulation we call it the empirical likelihood of D. A.1.1. Simulation details There are three parts to the simulation. Firstly we must specify the value of D. Secondly, we must repeatedly generate nc random DNA profiles and combine them together subject to

135

drop-out. Finally we must consider that contamination may have occurred. Each iteration of the simulation (for a given value of D) will produce a random profile that could have resulted from the contribution of nc unrelated individuals profiles, and from this profile we can count the number of observed alleles, x. Note that because we are not considering quantitative information such as peak heights or areas, it is possible for allele masking to occur. For example, if nc = 2 and two random profiles are ab and bc, we will only observe abc in the resulting scene stain. Hence, even with no drop-out (Pr(D) = 0), it is possible to observe fewer than 2ncL alleles. The frequency with which different values of x occur for a given value of D is estimate of Pr(xjD). A.1.2. Simulation pseudo-code Descriptions of simulations are always problematic. For that reason, we describe out simulation in pseudo-code so that those who are interested may replicate the work. for D = 0.0, 0.01, 0.02, . . ., 0.90 let ˜ f ¼ ½0; . . . ; 0, where ˜ f is a vector of length (2nc + 1)L + 1 for i = 1, . . ., N Make the scene profile blank for j = 1, . . ., nc for l = 1, . . ., L Select two alleles at random, Al1, Al2 with probability pAlk , k = 1, 2 Generate two random uniform numbers, u1, u2 U[0, 1] If u1 D then add allele Al1 to the scene profile If u2 D then add allele Al2 to the scene profile for l = 1, . . ., L Generate a random uniform number, u U[0, 1] If u Pr(C) add a random allele Al1, selected with probability pAl1 to the scene profile Record x, the total number of alleles observed Let f x = f x + 1 (the elements of ˜ f are labelled 0 to (2nc + 1)L) let Pr(xjD) = ( f x/N), x = 0, 1, . . ., (2nc + 1)L

where L is the number of loci in the multiplex (L = 10 for SGM+), N is the number of iterations per value of D. Increasing N will reduce the Monte Carlo sampling error in px. pAlk is the frequency of the kth allele at the lth locus in the population database. Note that usage above just means we select alleles randomly with probability proportional to their frequency in the database (population). The range of x is from 0 to (2n + 1)L because each individual can contribute at most two distinct peaks and furthermore we allow at least one contaminant allele per locus which may also be distinct. So when n = 2, there is a possibility that we will observe 0, . . ., 5 peaks and 0, . . ., 50 peaks over 10 loci.

Fig. 2. The likelihood surface for the probability of drop-out, given two contributors and Pr(C) = 0.05.

A.1.3. Simulation results Fig. 2 shows the likelihood surface for the probability of drop-out, given two contributors (nc = 2) and Pr(C) = 0.05. How is this used? This is best demonstrated by example. Consider the case in Section 5. A total of 32 alleles were observed across ten loci. Let us initially postulate that there were only two contributors to this profile. If x is constant, at 32, then the graph in Fig. 1 lets us answer the question ‘‘what is the most likely value for Pr(D) if x = 32?’’ We do this taking a

136


Fig. 3. Likelihood function for the probability of drop-out when x = 32 and nc = 2.

‘‘slice’’ of Fig. 1 along the line x = 32. This yields the graph in Fig. 3. From Fig. 3 we can see the maximum occurs when Pr(D) = 0. This means that 32 alleles are not uncommon when there is no drop-out and two contributors to the stain. However, we can see that it is also quite probable that we would observe 32 alleles even if Pr(D) = 0.2. Actually it is about 16 times less likely, but the point we wish to make is that it is not impossible to observe 32 alleles when Pr(D) = 0.2. Therefore, what we would like to do is put some sort of confidence bound on Pr(D). That is, we would choose a value D* so that 95% of intervals of the form [0, D*] would contain the true value. Although we use 95% in as an example throughout this paper there is no reason why a more stringent value (e.g. 99.9%) could not be used. To do this we need to estimate the cumulative distribution function (cdf) for the probability of drop-out given a certain value of x. We can change the likelihood function in Fig. 3 to a probability function by normalising it—i.e. making sure that the area under the curve sums to one (Fig. 4). In doing this, we are making the assumption that the probability of drop-out is a discrete random variable.1 In theory it is not, but in practice if we know the probability of drop-out to the nearest 1% (0.01) then this will be sufficient to calculate the LR without substantial bias to the defendant. Once we have the probability function for D, f(Djx), we can calculate the cumulative distribution function: FðDjxÞ ¼

d¼D X

f ðD ¼ djxÞ

d 2 f0;0:01;0:02;...g

The actual level of drop-out used in the LR calculations was taken from the 5th or 95th percentile of the cdf, dependent upon 1

And we are implicitly placing a uniform prior on it as well. Technically the normalization of the likelihood is a Bayesian operation, hence the interpretation of the resulting intervals are correct in a Bayesian sense.

Fig. 4. The cumulative distribution function (cdf) F(Djx = 32) for a profile with 32 alleles. The solid line is the cdf for D assuming that there are three (nc = 3) contributors to this mixture, whereas the dashed line is the cdf for D assuming that there are two (nc = 2) contributors. The y-axis tells us the probability that D is smaller than the value on the x-axis. For example, if a vertical line from the xaxis is drawn at the point 0.16 to where it hits the dashed line, and a horizontal line to the y-axis, it hits at about 0.95. We interpret this as ‘‘assuming only two people contributed to this mix, we are 95% sure that the true value of Pr(D) is less than 0.16.

the level that minimised the LR—in practice this is usually the 95th percentile. Mathematically we evaluate qa = F 1(a) where F 1(a) inverse cumulativeRdistribution function is given x by finding the value x such that 1 f ðtÞ dt ¼ a. a = 0.05 for the 5th percentile and a = 0.95 for the 95th percentile. In practice we approximate the cdf as a piecewise linear function. We find two points q1 and q2, such that F(q1) < a < F(q2) and we return F 1 ðaÞ wq1 þ ð1 wÞq2 where w ¼ ða Fðq1 ÞÞ=ðFðq2 Þ Fðq1 ÞÞ. In our example this yields values of 0.16 and 0.38. Appendix B. A more detailed example of LoComatioN principles In LoComatioN [12] the Q allele designation enables probabilistic evaluation of all possible allelic combinations, including those that could be explained if drop-out and contamination had happened. From the casework example, we evaluate all possible allele propositions for each locus in turn. For example for the case stain evidence (E) at the D3 locus we have two identical results: R1 = R2 = 14,16. The suspect, S, has genotype 14,16 and the victim V, has genotype 16,16. The propositions under consideration are: Hp: the victim, suspect and one unknown unrelated contributor are the only people who have contributed to this stain (V + S + U); Hd: the victim and two unknown unrelated contributors are the only people who have contributed to this stain (V + U1 + U2).


137

Table 6 Illustration of probabilistic principles employed to formulate the probabilities under Hp Proposed contributing genotypes V + S + U

Pr(R1 = 14,16jMj)

Pr(R2 = 14,16jMj)

Pr(Mj)

Product

16,16 + 14,16 + 14,14

No drop-out, no ¯ ¯ 6 PrðCÞ contamination PrðDÞ 6 ¯ ¯ PrðCÞ PrðDÞ ¯ ¯ 6 PrðCÞ PrðDÞ No drop-out, drop-out and ¯ ¯ 5 PrðDÞPrðCÞ contamination PrðDÞ 5 ¯ ¯ PrðDÞPrðCÞ PrðDÞ ¯ ¯ 4 PrðDÞPrðCÞ PrðDÞ

No drop-out, no ¯ ¯ 6 PrðCÞ contamination PrðDÞ 6 ¯ ¯ PrðCÞ PrðDÞ ¯ ¯ 6 PrðCÞ PrðDÞ No drop-out, drop-out and ¯ ¯ 5 PrðDÞPrðCÞ contamination PrðDÞ 5 ¯ ¯ PrðDÞPrðCÞ PrðDÞ ¯ ¯ 4 PrðDÞPrðCÞ PrðDÞ

p314 p316

¯ 2 p314 p316 ¯ 12 PrðCÞ PrðDÞ

2 p214 p416 p14 p516 2 p214 p316 pQ

¯ 2 p214 p416 ¯ 12 PrðCÞ 2PrðDÞ 12 ¯ ¯ PrðDÞ PrðCÞ2 p14 p516 ¯ 2 p214 p316 pQ ¯ 10 PrðDÞ2 PrðCÞ 2PrðDÞ

2 p14 p416 pQ p14 p316 p2Q

¯ 2 p14 p416 pQ ¯ 10 PrðDÞ2 PrðCÞ 2PrðDÞ 8 4 ¯ 2 p14 p316 p2Q ¯ PrðDÞ PrðCÞ PrðDÞ

16,16 + 14,16 + 14,16 16,16 + 14,16 + 16,16 16,16 + 14.16 + 14,Q 16,16 + 14,16 + 16,Q 16,16 + 14,16 + Q,Q

The numerator is then calculated by summing the entire product column, using the total law of probability.

Evaluation of the probability of the evidence under Hp is straight-forward – the unknown contributor, U, is allowed to have a genotype formed by any combination of alleles 14, 16 and Q – allowing for the possibility of drop-out to be considered. Hence, the genotypes considered for the unknown contributor, under Hp, would be: 14,14; 14,16; 16,16; 14,Q; 16,Q; Q,Q.

In order to illustrate the probabilistic principles employed in the software, the calculations have been formulated for the Hp alternatives in Table 6. The Hd calculations proceed in a similar fashion, however under Hd there are two unknown contributors, making the list of possible alternative genotypes for U1 and U2 a great deal longer, see Fig. 5 for allele combination listings. The following

Fig. 5. LoComatioN screen-shot showing some of the allelic combinations to be considered under Hp: V + S + U and Hd: V + U1 + U2 from a casework example (Table 2) LR = Pr(EjHp)/Pr(EjHd). Under Hd, all potential genotypes from U1 + U2 contributors are considered.

138


Table 7 Expansion of the first four rows of Fig. 5, to illustrate probabilistic principles employed to formulate probabilities under Hd Proposed contributing genotypes V + U1 + U2

Pr(R1 = 14,16jMj)

Pr(R2 = 14,16jMj)

Pr(Mj)

Product

16,16 + 14,14 + 14,14

No drop-out, no ¯ ¯ 6 PrðCÞ contamination PrðDÞ 6 ¯ ¯ PrðCÞ PrðDÞ No drop-out, drop-out and ¯ ¯ 5 PrðDÞPrðCÞ no contamination PrðDÞ 4 2 ¯ ¯ PrðDÞ PrðCÞ PrðDÞ

No drop-out, no ¯ ¯ 6 PrðCÞ contamination PrðDÞ 6 ¯ ¯ PrðCÞ PrðDÞ No drop-out, drop-out and ¯ ¯ 5 PrðDÞPrðCÞ no contamination PrðDÞ 4 2 ¯ ¯ PrðDÞ PrðCÞ PrðDÞ

p514 p316

¯ 2 p514 p316 ¯ 12 PrðCÞ PrðDÞ

4 p414 p416 4 p414 p316 pQ

¯ 2 p414 p416 ¯ 12 PrðCÞ 4PrðDÞ 10 ¯ 2 p414 p316 pQ ¯ 4PrðDÞ PrðDÞ2 PrðCÞ

6 p314 p316 p2Q

¯ 2 p314 p316 p2Q ¯ 8 PrðDÞ4 PrðCÞ 6PrðDÞ

16,16 + 14,14 + 14,16 16,16 + 14,14 + 14,Q 16,16 + 14,14 + Q,Q

Table 7 has been included in order to demonstrate that the principles applied to Hp, also apply to Hd. References [1] I. Findlay, A. Taylor, P. Quirke, R. Frazier, A. Urquhart, DNA fingerprinting from single cells, Nature 389 (1997) 555–556. [2] P. Gill, R. Sparkes, C. Kimpton, Development of guidelines to designate alleles using an STR multiplex system, Forens. Sci. Int. 89 (1997) 185– 197. [3] J.P. Whitaker, E.A. Cotton, P. Gill, A comparison of the characteristics of profiles produced with the AMPFlSTR SGM Plus multiplex system for both standard and low copy number (LCN) STR DNA analysis, Forens. Sci. Int. 123 (2001) 215–223. [4] P. Gill, A. Kirkham, Development of a simulation model to assess the impact of contamination in casework using STRs, J. Forens. Sci. 49 (2004) 485–491. [5] M. Bill, P. Gill, J. Curran, T. Clayton, R. Pinchin, M. Healy, J. Buckleton, PENDULUM—a guideline based approach to the interpretation of STR mixtures, Forens. Sci. Int. 148 (2004) 181–189. [6] T.M. Clayton, J.P. Whitaker, R. Sparkes, P. Gill, Analysis and interpretation of mixed forensic stains using DNA STR profiling, Forens. Sci. Int. 91 (1998) 55–70. [7] P. Gill, R. Sparkes, R. Pinchin, T. Clayton, J. Whitaker, J. Buckleton, Interpreting simple STR mixtures using allele peak areas, Forens. Sci. Int. 91 (1998) 41–53. [8] P. Gill, J. Curran, K. Elliot, A graphical simulation model of the entire DNA process associated with the analysis of short tandem repeat loci, Nucleic Acids Res. 33 (2005) 632–643.

[9] P. Gill, J. Whitaker, C. Flaxman, N. Brown, J. Buckleton, An investigation of the rigor of interpretation rules for STRs derived from less than 100 pg of DNA, Forens. Sci. Int. 112 (2000) 17–40. [10] J. Buckleton, P. Gill, Low copy number, in: J. Buckleton, C.M. Triggs, J.S. Walsh (Eds.), Forensic DNA Evidence Interpretation, CRC Press, 2005, pp. 275–297. [11] P. Taberlet, S. Griffin, B. Goossens, S. Questiau, V. Manceau, N. Escaravage, L.P. Waits, J. Bouvet, Reliable genotyping of samples with very low DNA quantities using PCR, Nucleic Acids Res. 24 (1996) 3189–3194. [12] J.M. Curran, P. Gill, M.R. Bill, Interpretation of repeat measurement DNA evidence allowing for multiple contributors and population substructure, Forens. Sci. Int. 148 (2005) 47–53. [13] C.H. Brenner, R. Fimmers, M.P. Baur, Likelihood ratios for mixed stains when the number of donors cannot be agreed, Int. J. Legal Med. 109 (1996) 218–219. [14] B.S. Weir, DNA statistics in the Simpson matter, Nat. Genet. 11 (1995) 365–368. [15] J. Buckleton, J.M. Curran, P. Gill, Towards understanding the effect of uncertainty in the number of contributors to DNA stains, Forens. Sci. Int., in press. [16] I.W. Evett, G. Jackson, J.A. Lambert, More on the hierarchy of propositions: exploring the distinction between explanations and propositions, Sci. Justice 40 (2000) 3–10. [17] R. Cook, I.W. Evett, G. Jackson, P.J. Jones, J.A. Lambert, A model for case assessment and interpretation, Sci. Justice 38 (1998) 151–156. [18] A. Lowe, C. Murray, J. Whitaker, G. Tully, P. Gill, The propensity of individuals to deposit DNA and secondary transfer of low level DNA from individuals to inert surfaces, Forens. Sci. Int. 129 (2002) 25–34. [19] I.W. Evett, C. Buffery, G. Willott, D. Stoney, A guide to interpreting single locus profiles of DNA mixtures in forensic cases, J. Forens. Sci. Soc. 31 (1991) 41–47.


Morphine and 6-acetylmorphine concentrations in blood, brain, spinal cord, bone marrow and bone after lethal acute or chronic diacetylmorphine administration to mice Emmanuelle Guillot a, Philippe de Mazancourt a, Michel Durigon b, Jean-Claude Alvarez a,* a

Laboratoire de Pharmacologie–Toxicologie, Centre Hospitalier Universitaire Raymond Poincare´, AP-HP, 104 Boulevard R. Poincare´, 92380 Garches, France b Service de Me´decine Le´gale, Centre Hospitalier Universitaire Raymond Poincare´, AP-HP, 104 Boulevard R. Poincare´, 92380 Garches, France Received 3 February 2006; received in revised form 23 March 2006; accepted 23 March 2006 Available online 24 May 2006

Abstract The aim of this study was to evaluate postmortem incorporation of opiates in bone and bone marrow after diacetylmorphine (heroin) administration to mice. Mice were given acute (lethal dose of 300 mg/kg) or chronic (10 and 20 mg/kg/24 h for 20 days) intraperitoneal administration of diacetylmorphine. The two metabolites of diacetylmorphine, 6-acetylmorphine (6-AM) and morphine, were extracted from whole blood, brain, spinal cord, bone marrow and bone (after hydrolysis) using a liquid/liquid method. Quantification was performed by gas chromatography–mass spectrometry (GC/MS). Results showed that after acute administration, opiates were present in all studied tissues. Morphine concentrations appeared to be higher than those of 6-AM in blood (52.4 mg/mL versus 27.7 mg/mL, n = 12), bone marrow (87.8 ng/mg versus 8.9 ng/mg, n = 6) and bone (0.85 ng/mg versus 0.43 ng/mg, n = 6), but 6-AM concentrations were higher than those of morphine in brain (14.0 ng/mg versus 7.4 ng/mg, n = 12) and spinal cord (27.8 ng/mg versus 20.8 ng/mg, n = 12). No correlation was found for both compounds between blood concentrations and either brain, spinal cord, bone or bone marrow concentrations while a significant one was found between brain and spinal cord concentrations either for morphine (r = 0.89, n = 12, p < 0.001) or 6-AM (r = 0.93, n = 12, p < 0.001), the concentration being higher in spinal cord than in brain. When bones were stored for 2 months, only 6-AM remained in bone marrow but not in bone. After chronic administration, mice being sacrificed by cervical dislocation 24 h after the last injection, no opiate was detected in any studied tissues. Further studies are required, in particular in human bones, but these results seem to show that 6-AM could be detect in bone marrow several weeks after the death and could be an alternative tissue for forensic toxicologist to detect a fatal diacetylmorphine overdose, even if no correlation between blood and bone marrow was observed. On the other hand, neither bone tissue nor bone marrow will allow the confirmation of a chronic diacetylmorphine use. # 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Bone; Bone marrow; Diacetylmorphine; Overdose; Toxicology

1. Introduction When bodies are extremely putrefied, specimens such as blood or urine are not available for forensic toxicologists to detect the presence of drugs or toxicological substances. Many studies have been carried out for a few years to find alternative tissues, which could remain available for detection of drugs a

* Corresponding author. Tel.: +33 1 47 10 79 38; fax: +33 1 47 10 79 23. E-mail address: [email protected] (J.-C. Alvarez). 0379-0738/$ – see front matter # 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.forsciint.2006.03.029

long time after death. Hair samples [1,2], nails [3] or teeth [4] have already been used for postmortem detection of opiates, as well as bone and bone marrow [5]. Diacetylmorphine is frequently involved in fatal overdose cases. It undergoes rapid esterase hydrolysis to 6-acetylmorphine (6-AM), which is further deacetylated to morphine [6]. Morphine is conjugated to morphine-3 and 6-glucuronide in humans, and preferentially to morphine-3-glucuronide in rats and mice [7]. Bone marrow has a rich vascular supply and a lipid matrix that may allow drug diffusion and incorporation from blood [8].

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E. Guillot et al. / Forensic Science International 166 (2007) 139–144

Moreover, it is encased in bone thus protecting it from possible contamination [9] or degradation. Several drugs including amitriptyline [8], metamphetamine and amphetamine [10], triazolam [11] and bromisovalum [12] have been detected and quantified in human bone marrow. Two conditions are required to ensure a diagnosis of fatal drug intoxication on bone marrow samples. First, a correlation between blood and bone marrow concentrations must be established, and secondly, bone marrow concentrations have to remain stable after death until the analysis is performed. A linear relationship between blood and bone marrow levels was found for several drugs by Winek et al. [13–15]. Moreover, metamphetamine and amphetamine concentrations in bone marrow collected from bones stored for 2 years in open air showed no drug degradation over this period [16]. However, a literature review showed a lack of available data about opiates. Drug detection in bone has only been studied in a few publications [5,17–19]. However, as with hair, drugs may remain trapped in bone for a long time. If so, it can be useful in determining a regular diacetylmorphine intake. Incorporation of benzodiazepines was reported in mice bone after chronic exposure, but not after acute administration [19]. In another study, determination of morphine in human postmortem bone and bone marrow was achieved, while 6-AM was not detected, due to bone demineralization procedure according to the authors [5]. Our preliminary hypotheses were that bone could be representative of chronic diacetylmorphine use, while bone marrow could be representative of diacetylmorphine overdose. So, the purpose of this study was to investigate the incorporation of opiates in bone and bone marrow after lethal acute or chronic diacetylmorphine injections to mice. In order to investigate any correlation between these tissues and blood or central nervous system, we also investigate the concentrations of morphine and 6-AM in blood, brain and spinal cord. Finally, we investigate the stability of the compounds in bone and bone marrow after 2 months. 2. Materials and methods 2.1. Experimental design Experiments were performed on 28 Swiss mice weighing 15 g, housed seven per cage under 12-h light:12-h dark cycle in a constant ambient temperature of 24 1 8C, with a free access to food and water (the principles of French laboratory animal care were followed). Animals received intraperitoneal injections of either saline (one control mouse per group) or diacetylmorphine hydrochloride (Euromedex, Mundolsheim, France) dissolved in saline (six mice per group). Two diacetylmorphine administration protocols were used in this study: - Acute administration: Two groups of six mice, respectively, received a lethal diacetylmorphine injection of 300 mg/kg. In the first group of animals, bone marrow samples were collected immediately. All samples (blood, brain, spinal cord,

marrow and pieces of bone) were frozen at 20 8C until analysis. In the second group, blood, brain and spinal cord were frozen immediately, but bones were stored in a jar containing 150 mL of non-sterile soil found in the forest. The bones were put on the soil and stored at room temperature. Two months later, dried bone marrow was collected and was frozen with bones. - Chronic administration: Two groups of six mice, respectively, received chronic diacetylmorphine injections of 10 or 20 mg/ kg every 24 h for 20 days. The animals were sacrificed on the 21st day, 24 h after the last administration, by cervical dislocation. Blood, brain, spinal cord, bones and bone marrow were collected and frozen at 20 8C until analysis. 2.2. Extraction procedures The gas chromatography–mass spectrometry (GC–MS) technique used in this study was adapted for each specimen from the procedure recommended by French Society of Analytical Toxicology [20] for the analysis of opiates in blood. 2.2.1. Chemicals Stock methanolic solutions of morphine (1.0 mg/mL), 6-AM (1.0 mg/mL), morphine-d3 (0.1 mg/mL) and 6-AM-d3 (0.1 mg/mL) were purchased from Promochem (Molsheim, France). Bistrimethylsilyltrifluoroacetamide (BSTFA)/trimethylchlorosilane (TMCS) (99/1, v/v) was purchased from Supelco (Bellefonte, USA). Other chemicals used were of chromatographic or analytical grade. 2.2.2. Extraction procedure in blood, brain, spinal cord and bone marrow Weighed bone marrow, brain and spinal cord were diluted and homogenized with an Ultraturax in 0.5 mL of deionized water for bone marrow and spinal cord and 4 mL for brain. To 500 mL of whole blood, brain, spinal cord or bone marrow homogenates were added 12.5 mL of 10 mg/L methanolic solution of internal standards (IS) (morphine-d3, 6-AM-d3), 1 mL of 2 M phosphate buffer pH 8.4 and 8 mL of chloroform/isopropanol/n-heptane: 50/17/33 (v/v/v). The preparation was shaken for 15 min and centrifuged at 3500 g for 5 min. The aqueous layer was discarded and the solvent layer was extracted by 5 mL of 0.2 M HCl. The aqueous layer obtained after agitation and centrifugation was neutralized by 1 mL of 1 M NaOH and re-extracted by 2 mL of phosphate buffer pH 8.4 and 5 mL chloroform. After agitation and centrifugation, the organic phase was evaporated under a nitrogen stream. Finally, the extract was derivatized by addition of 20 mL of BSTFA/TMCS and 30 mL of ethylacetate and heated at 70 8C for 30 min. Two microliters of the resulting solution were injected into the GC column. 2.2.3. Extraction procedure in bone Bone pieces were cleaned and boiled for 30 min to ensure that all bone marrow and muscle tissues had been removed. They were then ground in a mortar. To 50 mg of bone powder were added 25 mL of 10 mg/L IS methanolic solution and 1 mL


of 0.1 M HCl. The mixture was incubated at 55 8C for 12 h in order to perform bone hydrolysis. This hot acid hydrolysis was adapted from a method for the determination of hair opiates described by Kintz and Mangin [21]. One milliliter of 0.1 M NaOH was then added and the mixture was extracted using the procedure as described above. 2.3. Apparatus The GC/MS analysis was performed on a ThermoFinnigan GC 8060 Fisons equipped with a ThermoFinnigan mass spectrometer Automass II (electron impact mode). The capillary column used was a PTE 5 (30 m 0.25 mm i.d., 0.25 mm film thickness, Supelco, Bellefonte, USA). Samples were injected in the splitless mode at 250 8C. Temperature was programmed to rise from 90 8C (0.5 min) to 220 8C (30 8C/min, 3 min hold), and then to 290 8C (15 8C/min, 1 min hold). Transfer line and ion source temperatures were, respectively, 300 and 200 8C. Flow rate of the carrier gas (helium) was 2.1 mL/min. The ionization energy was 70 eV. The detection was in single ion monitoring mode at m/z 429 (quantification ion), 236 and 414 (confirmation ions) for morphine, and 399 (quantification ion), 340 and 287 (confirmation ions) for 6-AM. Ions at m/z 432, 239 and 417, and m/z 402, 343 and 290 were used for morphine-d3 and 6-AM-d3, respectively.

141

the peak-area of the compounds and the peak-area of their deuterated internal standards. The precision and accuracy of the method were carried out over 3 days in blood. Each day, two calibration curves with six determinations of three quality controls (20, 125 and 500 ng/ mL) were analyzed. The values obtained were analyzed using variance analysis (ANOVA), which separated the intradayassay and interday-assay standard deviations and consequently the corresponding coefficients of variation (CV). The intradayassay CV took into account the variability of the six replicates each day for 3 days and the interday-assay CV the variability of the days of analysis. The accuracy was determined by comparing the mean calculated concentration with the spiked target concentration of the quality control samples. The limit of detection (LOD) was defined as the lowest concentration of the compounds that can be detected with a signal-to-noise ratio greater than 5:1. The limit of quantification (LOQ) was defined as the lowest concentration of the analytes that can be quantified with both an accuracy of 10% of the spiked value and a coefficient of variation (CV) 20%. Extraction recoveries were estimated at 200 ng/mL (n = 6), and selectivity of the method was evaluated by analyzing blank blood and tissues (mice controls) by the described method. 2.5. Statistical analysis All samples were analyzed only once, because of the small amounts of samples collected from mice. Statistical analysis was performed using correlation test and unpaired Student’s t-test.

2.4. Method validation Two working solutions (10 and 1.0 mg/L) containing morphine and 6-AM were prepared by appropriate dilutions of stock solution in methanol. The working solution of morphine-d3 and 6-AM-d3 (IS) was prepared in methanol at 10 mg/L. All stock and working solutions were stored at 20 8C for a maximum of 3 months and 1 month, respectively. For linearity study, calibration curves were prepared by spiking six drug-free whole bloods (0.5 mL) with appropriate volumes of working solutions containing morphine and 6-AM (range 10–1000 ng/mL), or by spiking 50 mg of blank bone powder (range 0.25–20 ng/mg). Brain, spinal cord and bone marrow concentrations were determined with blood calibration curves. Quantification was performed by calculating the ratio between

3. Results Calibration curves were found to be linear in blood within the range 10–1000 ng/mL, with correlation coefficients being 0.995 for morphine and 0.992 for 6-AM. Linearity was also established in bone within the range 0.25–20 ng/mg. The LOD for both compounds were set at 3 ng/mL for blood analysis and 0.1 ng/mg for bone analysis, and the LOQ were set at 10 ng/mL and 0.25 ng/mg in blood and bone, respectively. The results of intra and inter-assay precision and accuracy of the method are presented in Table 1. The intra-assay coefficients of variation (CVs) were less than 6%, and the inter-assay coefficients of

Table 1 Intra- and inter-assay precision and accuracy of the method in blood Added (ng/mL)

Mean concentration found (ng/mL)

Accuracy (%)

Intra-assay CV (%)

Inter-assay CV (%)

Morphine 20 125 500

20.65 124.64 495.05

103.2 99.7 99.0

5.78 1.81 2.98

10.88 3.59 5.07

6-AM 20 125 500

20.13 122.73 492.62

100.7 98.2 98.5

4.82 4.20 2.98

10.87 8.85 4.08

Each day during 3 days, two calibration curves with six determinations of the three quality control samples (20, 125 and 500 ng/mL) were analyzed. The values obtained were analyzed using variance analysis (ANOVA).

142


Table 2 Morphine and 6-AM concentrations in blood (samples were diluted 1:100), brain, spinal cord, bone marrow and bone after acute lethal diacetylmorphine administration Mouse

1 2 3 4 5 6

Blood (mg/mL)

Brain (ng/mg)

Spinal cord (ng/mg)

Bone marrow (ng/mg)

Bone (ng/mg)

Morphine

6-AM

Morphine

6-AM

Morphine

6-AM

Morphine

6-AM

Morphine

6-AM

19.8 10.8 40.3 17.6 88.0 44.8

7.1 8.1 11.4 6.7 16.7 36.7

2.7 3.2 12 9.3 8.9 17.3

2.7 1.3 13 7.9 16 12

1.8 3.5 17.7 13 17.7 27.5

69 34 220 58 112 34

4.95 5.5 24 2.4 10 6.8

1.9 0.4 1.2 0.4 0.83 0.43

0.30 0.26 0.60 0.38 0.72 0.30

6 0.85 0.24

6 0.43 0.08

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