Forensic Analysis of Explosives Using Isotope Ratio Mass Spectrometry (IRMS)—Part 1: Instrument Validation of the DELTAplusXP IRMS for Bulk Nitrogen Isotope Ratio Measurements

Abstract: A significant amount of research has been conducted into the use of stable isotopes to assist in determining the origin of various materials. The research conducted in the forensic field shows the potential of isotope ratio mass spectrometry (IRMS) to provide a level of discrimination not achievable utilizing traditional forensic techniques. Despite the research there have been few, if any, publications addressing the validation and measurement uncertainty of the technique for forensic applications. This study, the first in a planned series, presents validation data for the measurement of bulk nitrogen isotope ratios in ammonium nitrate (AN) using the DELTA^plusXP (Thermo Finnigan) IRMS instrument equipped with a ConFlo III interface and FlashEA? 1112 elemental analyzer (EA). Appropriate laboratory standards, analytical methods and correction calculations were developed and evaluated. A validation protocol was developed in line with the guidelines provided by the National Association of Testing Authorities, Australia (NATA). Performance characteristics including: accuracy, precision/repeatability, reproducibility/ruggedness, robustness, linear range, and measurement uncertainty were evaluated for the measurement of nitrogen isotope ratios in AN. AN (99.5%) and ammonium thiocyanate (99.99+%) were determined to be the most suitable laboratory standards and were calibrated against international standards (certified reference materials). All performance characteristics were within an acceptable range when potential uncertainties, including the manufacturer’s uncertainty of the technique and standards, were taken into account. The experiments described in this article could be used as a model for validation of other instruments for similar purposes. Later studies in this series will address the more general issue of demonstrating that the IRMS technique is scientifically sound and fit‐for‐purpose in the forensic explosives analysis field.     

On the use of IRMS in forensic science: proposals for a methodological approach

The flourishing number of publications on the use of isotope ratio mass spectrometry (IRMS) in forensic science denotes the enthusiasm and the attraction generated by this technology. IRMS has demonstrated its potential to distinguish chemically identical compounds coming from different sources. Despite the numerous applications of IRMS to a wide range of forensic materials, its implementation in a forensic framework is less straightforward than it appears. In addition, each laboratory has developed its own strategy of analysis on calibration, sequence design, standards utilisation and data treatment without a clear consensus. Through the experience acquired from research undertaken in different forensic fields, we propose a methodological framework of the whole process using IRMS methods. We emphasize the importance of considering isotopic results as part of a whole approach, when applying this technology to a particular forensic issue. The process is divided into six different steps, which should be considered for a thoughtful and relevant application. The dissection of this process into fundamental steps, further detailed, enables a better understanding of the essential, though not exhaustive, factors that have to be considered in order to obtain results of quality and sufficiently robust to proceed to retrospective analyses or interlaboratory comparisons.     

Provenance Establishment of Stingless Bee Honey Using Multi‐element Analysis in Combination with Chemometrics Techniques

As consumption of stingless bee honey has been gaining popularity in many countries including Malaysia, ability to identify accurately its geographical origin proves pertinent for investigating fraudulent activities for consumer protection. Because a chemical signature can be location‐specific, multi‐element distribution patterns may prove useful for provenancing such product. Using the inductively coupled‐plasma optical emission spectrometer as well as principal component analysis (PCA) and linear discriminant analysis (LDA), the distributions of multi‐elements in stingless bee honey collected at four different geographical locations (North, West, East, and South) in Johor, Malaysia, were investigated. While cross‐validation using PCA demonstrated 87.0% correct classification rate, the same was improved (96.2%) with the use of LDA, indicating that discrimination was possible for the different geographical regions. Therefore, utilization of multi‐element analysis coupled with chemometrics techniques for assigning the provenance of stingless bee honeys for forensic applications is supported.     

Forensic analysis of explosives using isotope ratio mass spectrometry (IRMS) — Preliminary study on TATP and PETN

The application of isotopic techniques to investigations requiring the provision of evidence to a Court is limited. The objective of this research was to investigate the application of light stable isotopes and isotope ratio mass spectrometry (IRMS) to solve complex forensic cases by providing a level of discrimination not achievable utilising traditional forensic techniques.Due to the current threat of organic peroxide explosives, such as triacetone triperoxide (TATP), research was undertaken to determine the potential of IRMS to differentiate samples of TATP that had been manufactured utilising different starting materials and/or manufacturing processes. In addition, due to the prevalence of pentaerythritoltetranitrate (PETN) in detonators, detonating cord, and boosters, the potential of the IRMS technique to differentiate PETN samples from different sources was also investigated.Carbon isotope values were measured in fourteen TATP samples, with three definite groups appearing in the initial sample set based on the carbon data alone. Four additional TATP samples (in a second set of samples) were distinguishable utilising the carbon and hydrogen isotopic compositions individually, and also in combination with the oxygen isotope values. The 3D plot of the carbon, oxygen and hydrogen data demonstrated the clear discrimination of the four samples of TATP. The carbon and nitrogen isotope values measured from fifteen PETN samples, allowed samples from different sources to be readily discriminated.This paper demonstrates the successful application of IRMS to the analysis of explosives of forensic interest to assist in discriminating samples from different sources. This research represents a preliminary evaluation of the IRMS technique for the measurement of stable isotope values in TATP and PETN samples, and supports the dedication of resources for a full evaluation of this application in order to achieve Court reportable IRMS results.     

The Potential of Isotope Ratio Mass Spectrometry (IRMS) and Gas Chromatography‐IRMS Analysis of Triacetone Triperoxide in Forensic Explosives Investigations

Studying links between triacetone triperoxide (TATP) samples from crime scenes and suspects can assist in criminal investigations. Isotope ratio mass spectrometry (IRMS) and gas chromatography (GC)‐IRMS were used to measure the isotopic compositions of TATP and its precursors acetone and hydrogen peroxide. In total, 31 TATP samples were synthesized with different raw material combinations and reaction conditions. For carbon, a good differentiation and a linear relationship were observed for acetone–TATP combinations. The extent of negative (δ¹³C) fractionation depended on the reaction yield. Limited enrichment was observed for the hydrogen isotope (δ²H) values of the TATP samples probably due to a constant exchange of hydrogen atoms in aqueous solution. For oxygen (δ¹⁸O), the small isotopic range and excess of water in hydrogen peroxide resulted in poor differentiation. GC‐IRMS and IRMS data were comparable except for one TATP sample prepared with high acid concentration demonstrating the potential of compound‐specific isotope analysis. Carbon IRMS has practical use in forensic TATP investigations.     

Detection of counterfeit antiviral drug Heptodin™ and classification of counterfeits using isotope amount ratio measurements by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) and isotope ratio mass spectrometry (IRMS)

Isotope ratio mass spectrometry (IRMS) and multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) are highly important techniques that can provide forensic evidence that otherwise would not be available. MC-ICP-MS has proved to be a very powerful tool for measuring high precision and accuracy isotope amount ratios. In this work, the potential of combining isotope amount ratio measurements performed by MC-ICP-MS and IRMS for the detection of counterfeit pharmaceutical tablets has been investigated.An extensive study for the antiviral drug Heptodin™ has been performed for several isotopic ratios combining MC-ICP-MS and an elemental analyser EA-IRMS for stable isotope amount ratio measurements. The study has been carried out for 139 batches of the antiviral drug and analyses have been performed for C, S, N and Mg isotope ratios. Authenticity ranges have been obtained for each isotopic system and combined to generate a unique multi-isotopic pattern only present in the genuine tablets. Counterfeit tablets have then been identified as those tablets with an isotopic fingerprint outside the genuine isotopic range.The combination of those two techniques has therefore great potential for pharmaceutical counterfeit detection. A much greater power of discrimination is obtained when at least three isotopic systems are combined. The data from these studies could be presented as evidence in court and therefore methods need to be validated to support their credibility. It is also crucial to be able to produce uncertainty values associated to the isotope amount ratio measurements so that significant differences can be identified and the genuineness of a sample can be assessed.     

DNA barcoding as a tool for species identification in three forensic wildlife cases in South Africa

Poaching of wildlife animals for subsistence and commercial purposes has lead to population declines in Africa. In forensic cases, a need exists to identify the species of origin of carcasses, meat or blood. In the study presented here, the mitochondrial COI gene was sequenced to determine the species of unknown samples in three suspect South African forensic wildlife cases. In two cases the unknown samples were identified as originating from domestic cattle (Bos taurus) and in the third case the sample was identified as common reedbuck (Redunca arundinum). This is the first report of the COI sequence of common reedbuck. The study highlights the need for accurate wildlife reference material from each country in order to convict wildlife cases.     

DNA evidence in South Africa: Lessons learned to date

A trend was noted over the past 15 years in the South African courts. This trend has a multi-factorial origin and highlights the problems faced in the use of forensic science evidence in court. Although there have been improvements on how DNA evidence is gathered and presented in court, due to the fact that certain cases have been contested at the DNA evidence level, multiple issues remain that have not yet been addressed when DNA evidence is submitted to court. These issues include: accreditation, regulation of the forensic science profession, continued education, training of court officials, quality assurance, biased testimony, lack of transparency with regard to processes and procedures followed in the forensic community, incorrect interpretation of DNA evidence, lack of scientific knowledge (including the scientific method) by DNA experts, awareness by the legal profession and an over emphasis on the prosecuting perspective. These same aspects continue to plague current cases. Despite the above, the window of opportunity to address the above has not yet passed. However, it will take continuous and concerted efforts from the scientific and legal professions to bring about the appropriate change to facilitate justice for all in South Africa.     

Forensic genetic value of 27 Y-STR loci (Y-Filer® Plus) in the South African population

South Africa has one of the highest rape statistics in the world, with an average of 117 rapes reported daily. Y-STR genotyping is becoming a popular tool in the analysis of DNA evidence collected after a crime of a sexual nature has been committed, but has yet to be implemented in South Africa’s forensic laboratories. This study aimed to investigate the forensic value of the 27 Yfiler™ Plus loci in the South African population. A total of 271 samples from the African, Asian/Indian, Mixed Ancestry¹, and Caucasian populations at the University of the Free State in Bloemfontein, South Africa were amplified and analysed using ThermoFisher Scientific’s Yfiler™ Plus PCR Amplification kit. Of the 271 samples, 261 were identified to be unique, with an overall discrimination capacity of 98.15%. Discrimination capacities ranged from 91.67% for the Asian/Indian population to 100% for the Mixed Ancestry population. The haplotype diversity across the four populations is 0.9999, with an average gene diversity across all loci of 0.717. The forensic parameters estimated in this study provide evidence for the potential use of the commercial Yfiler™ Plus PCR amplification kit in a forensic application in South Africa.     

Stable isotope analysis of white paints and likelihood ratios

Architectural paints are commonly found as trace evidence at scenes of crime. Currently the most widely used technique for the analysis of architectural paints is Fourier Transformed Infra-Red Spectroscopy (FTIR). There are, however, limitations to the forensic analysis of white paints, and the ability to discriminate between samples.Isotope ratio mass spectrometry (IRMS) has been investigated as a potential tool for the analysis of architectural white paints, where no preparation of samples prior to analysis is required. When stable isotope profiles (SIPs) are compared, there appears to be no relationship between paints from the same manufacturer, or between paints of the same type. Unlike existing techniques, IRMS does not differentiate resin samples solely on the basis of modifier or oil-type, but exploits additional factors linked to samples such as geo-location where oils added to alkyd formulations were grown. In combination with the use of likelihood ratios, IRMS shows potential, with a false positive rate of 2.6% from a total of 1275 comparisons.     

Determination of sex and race from the subpubic angle in Ugandan subjects

The accurate determination of sex and race are important tools to forensic and physical anthropologists. In this study, the sex and race of 205 adult Ugandans were determined from the antero-posterior radiographs of the pelvis by measuring their subpubic angles. The angle ranged from 50 to 140 degrees with a mean of 93.86 degrees and standard deviation (SD) of 21.12 degrees for males and 75 to 155 degrees with a mean of 116.11 degrees (SD, 17.79 degrees) for females. The angle was significantly wider in women than men (P < 0.05), as indeed has previously been shown in other population groups studied. Using the demarking point method, 31.82% of Ugandan men and 10.53% of Ugandan women could be accurately sexed. However, more Malawians of both sexes previously studied had lower values for the angle and could be more accurately sexed. This study has also documented regional and racial variability of this angle among different population groups previously documented. Using the watershed subpubic angle derived from the means of this study and those of previously documented studies, 63% of Ugandans and 71% of Malawians could be accurately assigned to the black race. This method is recommended to physical and forensic anthropologists in the developing world.     

Background survey of polyethylene in the Australian Capital Territory – A demonstration of variability in isotopic abundance values and their application to forensic casework

Plastics including adhesive tapes, cable ties, and packaging are common evidence types encountered in forensic investigations and casework. Traditional examination techniques such as Fourier Transform Infrared (FTIR) spectroscopy lack specificity and are unable to discern differences within the same polymer structures leaving the analyst with a generic identification. High quality manufacturing methods further amplify the limitations in detecting variability between samples. Isotope Ratio Mass Spectrometry (IRMS) has been shown to be a valuable technique in further discriminating plastics. Discrimination is achieved by analysing the relative abundances of stable isotopes within a sample, with differences detected in isotope ratios possibly attributed to the source of raw materials and fractionation during the manufacturing process. A survey of cling wraps and re-sealable zipper storage bags collected in the Australian Capital Territory was undertaken to assess the variability in carbon and hydrogen isotope ratios of different brands and samples. The results of this research are discussed, particularly with respect to within and between brand trends, and a case study is presented as an example of the value of including IRMS in a casework context.     

Forensic science in South Africa: Status of the profession

The forensic science profession in South Africa is currently unregulated. There is also no national body that allows for the continued development or professional interaction of forensic scientists. The above has brought about a dire need to regulate the profession, in order to achieve the specific goals listed. To attain these objectives it is envisaged that the founding of a Forensic Science Academy in South Africa is of critical importance. The creation of a Forensic Science Academy was explored as the authors believe that such an Academy will provide structure to the profession of forensic science in South Africa – as well as paving the way towards regulation of the profession.     

海洛因来源鉴定的新方法

毒品来源的鉴定是指对毒品样品中包含的来源信息进行提取拜分析,这有助于打击毒品犯罪.海洛因是危害我国的主要毒品,它的来源鉴定更引起人们的关注.本文介绍了国际上研究海洛因来源的三种方法,即研究海洛因样品中的各种有机杂质及其相对比例;研究海洛因样品中的痕量无机元素;研究海洛因及吗啡的稳定同位素相对比值.第三种方法能够反映样品的地域性特点,因而在来源鉴定方面有突出的优势.气相色谱-燃烧-同位素比值质谱法是同位素比值测定方法中用于海洛因来源鉴定的最佳手段.这一技术还可用于其他微量物证(如炸药、药品、油品等)的来源鉴别,因而在法庭科学领域内显示了广阔的应用前景.     

Forensic analysis of explosives using isotope ratio mass spectrometry (IRMS) — Discrimination of ammonium nitrate sources

An evaluation was undertaken to determine if isotope ratio mass spectrometry (IRMS) could assist in the investigation of complex forensic cases by providing a level of discrimination not achievable utilising traditional forensic techniques. The focus of the research was on ammonium nitrate (AN), a common oxidiser used in improvised explosive mixtures.The potential value of IRMS to attribute Australian AN samples to the manufacturing source was demonstrated through the development of a preliminary AN classification scheme based on nitrogen isotopes. Although the discrimination utilising nitrogen isotopes alone was limited and only relevant to samples from the three Australian manufacturers during the evaluated time period, the classification scheme has potential as an investigative aid.Combining oxygen and hydrogen stable isotope values permitted the differentiation of AN prills from three different Australian manufacturers. Samples from five different overseas sources could be differentiated utilising a combination of the nitrogen, oxygen and hydrogen isotope values. Limited differentiation between Australian and overseas prills was achieved for the samples analysed.The comparison of nitrogen isotope values from intact AN prill samples with those from post-blast AN prill residues highlighted that the nitrogen isotopic composition of the prills was not maintained post-blast; hence, limiting the technique to analysis of un-reacted explosive material.     

Determination of sex from the clavicle and scapula in a Guatemalan contemporary rural indigenous population

The clavicle has been described as a useful bone for the metric determination of sex of human skeletal remains in a contemporary, predominantly white, North American forensic sample. In this article, measurements of clavicle and scapula are provided for a contemporary Guatemalan rural indigenous sample of forensic origin. Maximum length and circumference at midshaft of the clavicle, and height and width of the glenoid fossa of the scapula, were measured in 35 female and 62 male clavicles, and in 38 female and 65 male scapulae. Discriminant function analysis was used to study sexual dimorphism in this population with a classification purpose. Leave-one-out method (jackknife) matrices produced classification success rates ranging from 85.6% to 94.8%. A comparison with the North American forensic sample showed low percentages of correctly sexed Guatemalan male clavicles, ranging from 29.4% to 54.9%. The choice of an appropriate standard for the metric determination of sex is a crucial step in forensic anthropology.     

Discriminating sex in South African blacks using patella dimensions

For many years, sex determination has been carried out on skeletal remains to identify individuals in forensic cases and to assess populations in archaeological cases. Since it has been shown that not all bones are found in a forensic case, discriminant function equations should be derived for all bones of the body to assist in sex determination. Numerous studies have shown the usefulness of bones of the lower extremity (e.g. femur, tibia) in sex determination using discriminant function analysis, but the use of patella measurements has not been extensively investigated for this purpose. It is therefore the aim of this study to derive discriminant function equations for sex determination from measurements of the patella of South African blacks as represented in the Raymond A. Dart Collection of Human Skeletons. A total sample of 120 (60 male, 60 female) patellae were measured using six measurements. The Statistical Product and Service Solutions (SPSS) program was used to derive the equations. Stepwise and direct analyses were performed with the highest rate of classification of 85% thereby making the patella useful for sex determination. Thus, the proposed equations derived from this study should be used with caution and only on the South African black population group.     

Training of legal professionals in DNA evidence

The South African Criminal Legal System is based on Roman Dutch law. Court proceedings are led by a single presiding officer of the court. Prosecutors and defence advocates present the court with evidence in an adversarial manner. This system has inherent advantages and disadvantages and therefore the training of legal professionals in handling DNA evidence in court is important. The prosecutors resort under the National Prosecuting Authority and the defence advocates act independently or e.g. under the auspices of Legal Aid South Africa.Education curricula of legal professional do not include forensic science evidence. Principles such as evidential value in the forensic context are not addressed. Training of legal professionals with our Essential DNA Evidence™ Course has been a multiplier of forensic science knowledge in the legal profession in South Africa. We present prosecution and defence perspectives in an unbiased manner, compensating for the possible subjective interpretations of evidence that may be presented in court. Forensic evidence is subsequently carefully evaluated prior to being court presentation thus improving court efficiency, and allowing for a more focussed approach to the presentation of evidence. Approaches to the customisation of course content that adds value has been identified via evaluation of training programmes.Experience has shown that legal professionals have the ability to incorporate relatively complex scientific concepts into their legal arguments if provided with the appropriate training opportunity. Appropriate training in DNA evidence has made the court process more effective, both in terms of time and costs, and ultimately serves justice.     

Historical Trends in Graduate Research and Training of Diplomates of the American Board of Forensic Anthropology

The history of forensic anthropology has been documented by numerous scholars. These contributions have described the work of early pioneers in the field and have described important milestones, such as the founding of the Physical Anthropology Section of the American Academy of Forensic Sciences (AAFS) in 1972 and the American Board of Forensic Anthropology (ABFA) in 1977. This paper contributes to the growing literature on the history of forensic anthropology by documenting the academic training of all individuals who have been granted diplomate status by the ABFA (n = 115). Doctoral dissertation titles were queried to discern broad patterns of research foci. A total of 39 doctoral granting institutions have trained diplomates and 77.3% of board‐certified forensic anthropologists wrote dissertations involving skeletal biology, bioarchaeology, or forensic anthropology. Board‐certified forensic anthropologists are a broadly trained group of professionals with far‐reaching anthropological interests and expertise.