Routine Casework Research Articles

Emergence of Unique Tri-Allelic Patterns in Routine Casework Analysis at Punjab Forensic Science Agency, Pakistan, 2022–23

Emergence of Unique Tri-Allelic Patterns in Routine Casework Analysis at Punjab Forensic Science Agency, Pakistan, 2022–23

Comprehensive Evaluation of Cocaine and its Hydroxy Metabolites in Seized Cocaine and a Large Cohort of Hair Samples.

As cocaine is not only incorporated into hair via blood following ingestion but also by external contamination, hair samples are commonly tested for cocaine metabolites to prove ingestion. However, cocaine metabolites can also be present as degradation products in typical street cocaine samples. The present study investigates minor hydroxycocaine metabolites para- and meta-hydroxycocaine together with para- and meta-hydroxybenzoylecgonine in seized cocaine (n=200) and hair samples from routine casework (n=2,389). Analytical results of hair samples were interpreted using an established decision model for the differentiation between actual use and external contamination using metabolic ratios (metabolite to cocaine). They were further examined concerning background of request, hair color, body site of sample collection, sex, and metabolic ratios of the main metabolites (benzoylecgonine, norcocaine, and cocaethylene). All seized cocaine samples were positive for para- and meta-hydroxycocaine with a maximum percentage of 0.025 and 0.052 %, respectively; para- and meta-hydroxybenzoylecgonine were detected in 55 and 56 % of samples with a maximum percentage of 0.044 and 0.024 %, respectively. Analytical results of 424 hair samples (17.7 %) were interpreted as being predominantly from contamination; the majority of these samples were from traffic medicine cases (83.7 %). Metabolic ratios of minor hydroxycocaine metabolites were significantly higher in hair samples interpreted as originating from use than in samples interpreted as caused by contamination. Metabolic ratios for hydroxycocaines were significantly higher in forensic cases compared to abstinence controls and also in black hair compared to blond/gray hair. However, this was not the case for hydroxybenzoylecgonine metabolic ratios. No statistical difference was observed with regard to the donor's sex. Hydroxycocaine metabolic ratios increased significantly with increasing ratios of norcocaine and cocaethylene to cocaine, respectively. The study demonstrates that hydroxycocaine metabolites (including thresholds for their metabolic ratios) must be used for a reliable interpretation of positive cocaine results in hair samples.

How often do fingerprint examiners disagree in routine casework?

During routine casework, fingerprint examiners are required to make decisions pertaining to the sufficiency of friction ridge skin impressions. Prior experimental research has established that differences of opinion between examiners are expected, though it is uncertain if these findings are representative of the decisions made during casework. In this study, 5000 job-cards completed by fingerprint experts of the NSW Police Force were scrutinised to track the differences of opinion that occurred between examiners. Experts recorded 19,491 casework decisions, which resulted in 8964 reported identification and inconclusive determinations. Expert decision making was found to be unanimous in 94.8 % of these determinations; 4.6 % involved one expert-to-expert disagreement; and 0.5 % involved two expert-to-expert disagreements. Nil determinations featured more than two expert-to-expert disagreements. Expert-to-expert disagreements occurred in 3.7 % of all identification and inconclusive casework verification decisions. However, verifying experts were more likely to agree with a prior expert’s identification decision, than a prior expert’s inconclusive decision. The observed expert-to-expert identification disagreement rate was 2.0 %, whereas the observed expert-to-expert inconclusive disagreement rate was 12.5 %. Overall, most casework disagreements arose due to subjective differences concerning the suitability of friction ridge skin information for comparison or sufficiency for identification. Experts were more concordant in their decision-making with other experts than with trainees, and approximately three times more likely to disagree with a prior trainees’ identification or inconclusive decision than a prior experts’ identification or inconclusive decision. We assume these differences reflect trainees’ developing proficiencies in assessing the suitability or sufficiency of friction ridge skin impression information. Differences of opinion in casework are expected, which exposes the subjective nature of fingerprint decision-making. Computer-based quality metric and likelihood ratio tools should be considered for use in casework to guide examiner evaluations and mitigate examiner disagreements.

Developmental validation of the STRSeqTyper122 kit for massively parallel sequencing of forensic STRs.

Massively parallel sequencing allows for integrated genotyping of different types of forensic markers, which reduces DNA consumption, simplifies experimental processes, and provides additional sequence-based genetic information. The STRseqTyper122 kit genotypes 63 autosomal STRs, 16 X-STRs, 42 Y-STRs, and the Amelogenin locus. Amplicon sizes of 117 loci were below 300bp. In this study, MiSeq FGx sequencing metrics for STRseqTyper122 were presented. The genotyping accuracy of this kit was examined by comparing to certified genotypes of NIST standard reference materials and results from five capillary electrophoresis-based kits. The sensitivity of STRseqTyper122 reached 125pg, and > 80% of the loci were correctly called with 62.5pg and 31.25pg input genomic DNA. Repeatability, species specificity, and tolerance for DNA degradation and PCR inhibitors of this kit were also evaluated. STRseqTyper122 demonstrated reliable performance with routine case-work samples and provided a powerful tool for forensic applications.

Ethanol and Higher Alcohols' Production in Fungal and Bacterial Laboratory Cultures and Significance for Forensic Samples.

Ethanol can be produced by many microorganisms that colonize a dead body. Ethanol's concentration depends on the congener higher alcohols, 1-propanol, isobutanol, 2-methyl-1-butanol, 3-methyl-1-butanol, and 1-butanol, as previous research has shown. This correlation is expressed by mathematical models which estimate the concentration of microbial ethanol. The aim of this contribution was to study the ethanol and higher alcohols' production in various laboratory bacterial and fungal cultures and the applicability of the bacterial and fungal models (which concern the bacteria E. coli, S. aureus, K. pneumoniae, and E. faecalis, and the fungus C. albicans) in these samples, as well as in blood samples from autopsy cases, with the overall objective of investigating the models' applicability in routine casework. The bacteria and fungus were cultured in conventional culture media and in denatured human blood cultures under various conditions. The alcohols' concentrations were determined using a head space-gas chromatography-flame ionization detector (HS-GC-FID). The previously reported bacterial and yeast models were applied in the cultured samples and in blood from 122 autopsy cases. Our results showed that 1-propanol was not produced by C. albicans and E. faecalis under certain conditions. Also, 1-butanol was not produced by C. albicans, E. faecalis, and K. pneumonia under certain conditions. Furthermore, the bacterial models were applicable in postmortem samples irrespective of the microbes that were possibly activated in the sample, while the EC models showed the best applicability among all the bacterial and yeast models. The best applicability of the bacterial models was observed in autopsy blood with 0.10 g/L < BAC < 1.0 g/L in cases of violent and undetermined causes of death and in cases with putrefaction. Finally, the yeast models were applicable in limited, possibly special, autopsy cases. In conclusion, it could be inferred that the source of ethanol in any given postmortem blood sample is likely microbial if either most bacterial models or at least one model from each distinct bacterial species is successfully applicable.

Considerations on the application of a mutation model for Y-STR interpretation

If Y-STR profiling is to be more effective in criminal casework, the methods used to evaluate evidential weight require improvement. Many forensic scientists assign an evidential weight by estimating the number of times a Y-STR profile obtained from a questioned sample has been observed in YHRD datasets. More sophisticated models have been suggested but not yet implemented into routine casework, e.g. Andersen & Balding [1]. Mutation is inherent to STR meiosis (or inheritance) and is encountered in practice. We evaluated a mutation model that can be incorporated into a method for assigning evidential weight to Y-STR profiles, an essential part of bringing any method into practice. Since an important part of implementation to casework is communication, the article is written in an accessible format for practitioners as well as statisticians.The mutation component within the MUTEA model by Willems et al. [2] incorporates the potential for multistep mutations and a tendency for alleles to revert towards a central length, reflecting observed mutation data, e.g. [3]. We have estimated the parameters in this model and in a simplified symmetric version of this model, using sequence data from father/son pairs [4] and deep-rooted pedigrees [5]. Both datasets contain multistep mutations, which may have an effect on models based on simulations [1].We introduce Beta-Binomial and Beta-Geometric conjugate analyses for estimating rate and step parameters for the mutation models presented here, which require only summations and multiplications. We proved mathematically that the parameters can be estimated independently. We show the importance of reporting the variability of the parameters and not only a point estimate. The parameters can be easily incorporated into statistical models, and updated sequentially as more data becomes available. We recommend fuller publication of data to enable the development and evaluation of a wider range of mutation models.

Rare Allele 29 at Locus D2S1338 Observed During Routine Casework in Bulgarian Population

In this work, we report a rare allele 29 at locus D2S1338, established during routine forensic practice in a case of first-degree kinship (parenthood). This rare allele variant 29 at locus D2S1338, to the best of our knowledge, is reported for the first time for the Bulgarian population. So far it has not been registered in studies of allele frequencies in the same locus for 20 population groups in Europe and Asia. The presentation of similar genotyping findings relating to rare/unexpected population genetic variation is very important for the examination and documentation of such anomalies. The analysis has been performed for 16 STR loci: D2S1338, SE33, D16S539, D18S51, TH01, D12S391, D3S1358, FGA, vWA, D21S11, D1S1656, D2S441, D8S1179, D19S433, D22S1045, D10S1248 and 2 sex determination systems – Amelogenin and Y indel, set in NGM DetectTM PCR Amplification Kit (Applied Biosystems). The use of allelic witnesses in the diagnostic practice is mandatory in the standard fragment DNA analysis. The allelic witness contains well-known preset alleles for the examined locus. Establishing alleles that are outside the factory preset is of importance for broadening the scope of the witness and heightening the accuracy of the analysis. Rare allelic variants significantly increase the strength of discrimination when DNA profiles are compared. In this regard, it is important to report any new information about the emergence of rare allele variants detected in a particular population group.

Chemometrics in Forensic Chemistry – Part III: Quality assessment and interpretation of chemometric output

The number of samples sent to forensic laboratories as well as the complexity of the drug situation has increased tremendously during recent years. At the same time the amount of data gathered from chemical measurements has been mounting. This creates challenges for forensic chemists: how to handle the data, how to reliably answer the questions asked, and how to examine the data to find new properties or how to disclose connections with respect to source attribution of samples within a case or retrospective to past cases, stored in a database. Previously published articles Chemometrics in Forensic Chemistry – Part I and II discussed where in the forensic workflow of routine casework chemometrics is applied, and presented examples of chemometric methods used in cases of illicit drugs. This article explains through examples that the chemometric results must never stand-alone. Before such results are reported, quality assessment steps, which may consist of operational, chemical, and forensic assessments are required. In each case a forensic chemist needs to consider the suitability of chemometric methods, based on their strengths, weaknesses, opportunities and threats (SWOT). This is because while chemometric methods are powerful tools managing complex data, they are to some extent chemically blind.

Respiratory viruses in medicolegal autopsies during the winter season 2021/2022: observations after reduction of coronavirus disease-19 (COVID-19) pandemic restrictions

In the context of the coronavirus disease (COVID-19) pandemic, measures were taken to protect the population from infection. These were almost completely lifted in several countries in the spring of 2022. To obtain an overview of the spectrum of respiratory viruses encountered in autoptical routine case work, and their infectivity, all autopsy cases at the Institute of Legal Medicine in Frankfurt/M. with flu-like symptoms (among others) were examined for at least 16 different viruses via multiplex PCR and cell culture. Out of 24 cases, 10 were virus-positive in PCR: specifically, 8 cases with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), 1 with respiratory syncytial virus (RSV), and 1 with SARS-CoV-2 and the human coronavirus OC43 (HCoV-OC43), as a double infection. The RSV infection and one of the SARS-CoV-2 infections were only detected due to the autopsy. Two SARS-CoV-2 cases (postmortem interval of 8 and 10 days, respectively) showed infectious virus in cell culture; the 6 other cases did not show infectious virus. In the RSV case, virus isolation by cell culture was unsuccessful (Ct value of 23.15 for PCR on cryoconserved lung tissue). HCoV-OC43 was measured as non-infectious in cell culture, with a Ct value of 29.57. The detection of RSV and HCoV-OC43 infections may shed light on the relevance of respiratory viruses other than SARS-CoV-2 in postmortem settings; however, further, more extensive studies are needed for a robust assessment of the hazard potential due to infectious postmortem fluids and tissues in medicolegal autopsy settings.

What types of information can and do latent print examiners review? A survey of practicing examiners

Understanding typical work practices is important to understanding the decision-making process underlying latent print comparison and improving the reliability of the discipline. Despite efforts to standardize work practices, a growing literature has demonstrated that contextual effects can influence every aspect of the analytic process. However, very little is known about what types of information are available to latent print examiners, and what types of information latent print examiners routinely review. We surveyed practicing latent print examiners (N = 284) regarding what types of information are accessible during routine casework, and what types of information they routinely review during casework. We also explored whether access and inclination to review different types of information vary according to unit size and examiner role. Results indicated that information describing the physical evidence is accessible by almost all examiners (94.4%), and most examiners have access to offense type (90.5%), method of evidence collection (77.8%), and the names of both suspect (76.1%) and victim (73.9%). However, evidence description (86.3%) and method of evidence collection (68.3%) were the only information types consistently reviewed by most examiners. Findings also indicate that examiners in smaller laboratories have access to more information types and often review more information types than examiners from larger laboratories, but both populations choose to not review information at similar rates. Further, examiners in supervisory positions are more likely to choose to not review information than examiners in non-supervisory positions. Although there is some consensus regarding what types of information examiners routinely review, findings suggest that there is little absolute consensus regarding what information examiners can even access, and highlight two sources of variability in examiner work practices: employment setting and examiner role. This is concerning in light of efforts to maximize the reliability of analytic procedures (and ultimately, conclusions) and represents an important area of future study as the field progresses.

Novel Receptor-Binding-Based Assay for the Detection of Opioids in Human Urine Samples.

Consumption of opioids is a growing global health problem. The gold standard for drugs of abuse screening is immunochemical assays. However, this method comes with some disadvantages when screening for a wide variety of opioids. Detection of the binding of a compound at the human μ-opioid receptor (MOR) offers a promising alternative target. Here, we set up a urine assay to allow for detection of compounds that bind at the MOR, thus allowing the assay to be utilized as a screening tool for opioid intake. The assay is based on the incubation of MOR-containing cell membranes with the selective MOR-ligand DAMGO and urine. After filtration, the amount of DAMGO in the eluate is analyzed by liquid chromatography tandem mass spectroscopy (LC-MS/MS). The absence of DAMGO in the eluate corresponds to a competing MOR ligand in the urine sample, thus indicating opiate/opioid intake by the suspect. Sensitivity and specificity were determined by the analysis of 200 consecutive forensic routine casework urine samples. A pronounced displacement of DAMGO was observed in 29 of the 35 opiate/opioid-positive samples. Detection of fentanyl intake proved to be the most challenging aspect. Applying a cut-off value of, e.g., 10% DAMGO binding would lead to a sensitivity of 83% and a specificity of 95%. Consequently, the novel assay proved to be a promising screening tool for opiate/opioid presence in urine samples. The nontargeted approach and possible automation of the assay make it a promising alternative to conventional methods.

Microbiome-Based Stain Analyses in Crime Scenes.

Recent advances in next-generation sequencing technologies (NGS) coupled with machine learning have demonstrated the potential of microbiome-based analyses in applied areas such as clinical diagnostics and forensic sciences. Particularly in forensics, microbial markers in biological stains left at a crime scene can provide valuable information for the reconstruction of crime scene cases, as they contain information on bodily origin, the time since deposition, and donor(s) of the stain. Importantly, microbiome-based analyses provide a complementary or an alternative approach to current methods when these are limited or not feasible. Despite the promising results from recent research, microbiome-based stain analyses are not yet employed in routine casework. In this review, we highlight the two main gaps that need to be addressed before we can successfully integrate microbiome-based analyses in applied areas with a special focus on forensic casework: one is a comprehensive assessment of the method's strengths and limitations, and the other is the establishment of a standard operating procedure. For the latter, we provide a roadmap highlighting key decision steps and offering laboratory and bioinformatic workflow recommendations, while also delineating those aspects that require further testing. Our goal is to ultimately facilitate the streamlining of microbiome-based analyses within the existing forensic framework to provide alternate lines of evidence, thereby improving the quality of investigations.

Detecting DNA damage in stored blood samples

Several commercially available quantitative real-time PCR (qPCR) systems enable highly sensitive detection of human DNA and provide a degradation index (DI) to assess DNA quality. From routine casework in forensic genetics, it was observed that DNA degradation in forensic samples such as blood samples stored under sub-optimal conditions leads to visible effects in multiplex analyses of short tandem repeat markers (STRs) due to decreased amplification efficiencies in longer amplicons. It was further noticed that degradation indices often remain below the value that is considered to be critical. Thus, the aim of this work was to systematically analyze this effect and to compare conventional qPCR assays with a modified qPCR approach using uracil DNA glycosylase (UNG) and DNA quality assessment methods based on electrophoresis. Blood samples were stored at three different storage temperatures for up to 316 days. Significantly increased DNA recovery was observed from samples stored at high temperatures (37 °C) compared samples stored at room temperature and 4 °C. We observed typical effects of degradation in STR analyses but no correlation between DI and storage time in any of the storage conditions. Adding UNG slightly increased the sensitivity of detecting DNA degradation in one of the qPCR kits used in this study. This observation was not confirmed when using a second qPCR system. Electrophoretic systems did also not reveal significant correlations between integrity values and time. Methods for detecting DNA degradation are usually limited to the detection of DNA fragmentation, and we conclude that degradation affecting forensic STR typing is more complex.

Assessment of MDMA tablet and capsule dosages from seizures in Queensland, Australia

3,4-Methylenedioxymethamphetamine (MDMA) is prominent in the illicit drug market and usually presents as tablets, capsules, or crystal. Drug purity determinations are typically performed in the Forensic Chemistry, Queensland Health Forensic and Scientific Services (QHFSS) laboratory on homogenised samples, yielding an average MDMA concentration which can be used to calculate average MDMA dosages (mg) per unit (i.e., tablet or capsule). Little published research exists however regarding individual dosage variability and drug content of capsules and tablets in the Australian illicit drug market. This study assessed selected tablet and capsule submissions as a part of routine casework over an 18-month period primarily to examine MDMA dosage variations between tablets or capsules within the same exhibit. Additionally, dosage variations from different seizures of the same logo or appearance were investigated where possible. Generally, tablet exhibits were found to have consistent dosages however, there were several instances where large variations were noted. These dosage variations were often attributable to inconsistent tablet whole weights, compounded by differences in MDMA concentration within tablets. MDMA dosage differences in capsule presentations were generally due to differences in capsule contents weight with some instances of individual capsules recording double the MDMA dosage of other capsules in the same seizure. To complement this study, results from all available MDMA detections from 2017 to 2020 in the QHFSS laboratory were examined. Average MDMA concentrations within tablets, capsules and crystal presentations increased during that time. Correspondingly, average MDMA dosages increased within capsule and tablet presentations, noting there was still a substantial range of MDMA dosages observed within capsule and tablet presentations. Finally, the presence of adulterants (psychoactive or non-psychoactive) in combination with MDMA was reported in a small proportion of cases, and more frequently in tablets than capsules. This study has provided a comprehensive survey and highlights the potential dosage variability that may be encountered in MDMA presentations in Queensland.

DNA transfer between worn clothing and flooring surfaces with known histories of use

DNA samples recovered from items of clothing are often attributed to the wearer and one or more individuals who may have contacted the item during an alleged criminal activity. Another scenario often proposed by defence counsel is that DNA was transferred from a previously contacted item/surface unrelated to the activity of interest onto the item of clothing. Under such scenarios, DNA may also be transferred from the clothing to the item/surface with which it comes into contact. One such surface is flooring, upon which clothing may be placed while not being worn or may be contacted during wearing, such as falling or being forced to the ground. This study investigates the transfer of DNA to and from clothing and flooring when different contacts are applied between the two surfaces in an environment representative of what investigators would encounter in routine casework, a residential environment. Participants were provided with two sets of new and unused upper and lower garments to wash then wear for ~8 h inside their own home before storing them in paper evidence bags. The two sets of clothing were taken to a home occupied by unrelated individuals, where one set was placed on the floor (‘passive’) by the researcher while the other was worn by the participant who laid with their back on the floor, rolled to one side and back, then stood up (‘active’). Within the houses sampled, the main bedroom was targeted as flooring types and histories of use were more consistent across houses and less variation in DNA profile composition was previously observed for samples collected in the same room. Samples were collected from predetermined areas of the clothing and flooring where contact did and did not occur. Reference profiles were obtained from wearers and individuals they lived with, as well as occupants of the home. DNA transfer was observed from clothing to flooring and from flooring to clothing in both ‘active’ and ‘passive’ situations, though greater where a situation involved the application of pressure and friction (‘active’), and only where contact between clothing and flooring occurred. Results from this study inform on the composition of DNA profiles one is likely to obtain from an item of clothing or a flooring surface following a similar contact event between the two substrates and will aid investigators when interpreting DNA evidence recovered in a domestic environment and the activities leading to its transfer and subsequent recovery.

A novel receptor binding based assay to screen for opiates and (synthetic) opioids in human urine samples

Up to date there are, without knowledge of the compounds structure or utilization of antibodies, almost no comprehensive screening methods for the detection (synthetic) opioid uptake in urine samples available. Consequently, appearance of new opioids on the drug market require a tedious effort to update the present methods (e.g. ELISA or LC-MS/MS methods). Detection of the binding of a compound at the human μ-opioid receptor (MOR) offers a promising alternative analytical target as almost all of the opioids on the drug market take effect through binding at this receptor. Recently, we demonstrated that it is possible to accurately determine the binding of a compound (Ki value) at the MOR by LC MS/MS analysis rather than by radioactive detection methods. Here we set up the assay to allow for a detection of compounds that bind at the MOR in urine samples, thus allowing the assay to be utilised as a screening tool for opioid uptake. The assay is performed in a 96-well format and is based on the incubation of readily available cell membranes (prepared from CHO-K1 cells stably transfected with MOR) with the selective MOR-ligand DAMGO ([D-Ala2, N-MePhe4, Gly5-ol]-enkephalin) and 100 μL of urine for 60 minutes. After filtration and washing steps the amount of DAMGO in the eluate is analysed by a rapid and highly sensitive LC-MS/MS method on a QTRAP 6500+ system. Absence of DAMGO in the eluate corresponds to a competing MOR-ligand in the urine sample thus indicating opiate/opioid uptake by the suspect. Sensitivity and specificity was determined by the analysis 200 consecutive forensic routine casework urine samples (with known presence/absence of opiates and opioids determined by immunochemical assays, GC-MS and LC-Q-ToF screenings). DAMGO binding in the positive samples ranged from < 1% to 59% (Mean: 7%, Median: 3%). Twelve different opiates/opioids and/or there metabolites were present in 35 positive samples. A pronounced displacement (<10% DAMGO binding) was observed in 29 of the 35 samples. Detection of fentanyl uptake proved to be the most challenging analyte with 5 out of 10 positive samples showing an insufficient DAMGO displacement (14%–30% DAMGO binding, fentanyl concentration in these five sample: 1.0–5.7 ng/mL. Additionally, a urine sample containing 91 ng/mL tramadol and 42 ng/mL O-desmethyltramadol showed a poor displacement of DAMGO at the MOR. This can be explained by the low Ki values of the compounds at the MOR of 6014 and 40 nM, respectively. Among the nine false positive samples, no cluster of a particular compound was observed. Consequently, a cut-off value of 10% DAMGO binding would lead to a sensitivity of 83% and a specificity of 95% while a sensitivity of > 90% and a specificity of 88% would be achieved by applying a cut-off value of 17% DAMGO binding. The novel assay proved to be a suitable screening tool for opiate/opioid presence in urine samples. The non-targeted approach and possible automation of the assay make it a promising high throughput-capable alternative to conventional methods.

Blind testing in firearms: Preliminary results from a blind quality control program.

Open proficiency tests meet accreditation requirements and measure examiner competence but may not represent actual casework. In December 2015, the Houston Forensic Science Center began a blind quality control program in firearms examination. Mock cases are created to mimic routine casework so that examiners are unaware they are being tested. Once the blind case is assigned to an examiner, the evidence undergoes microscopic examination and comparison to determine whether the fired evidence submitted was fired in the same firearm. Fifty‐one firearms blind cases resulting in 570 analysis and comparison determinations were reported between December 2015 and June 2021. No unsatisfactory results were obtained; however, 40.3% of comparisons in which the ground truth was either elimination or identification resulted in inconclusive conclusions. Due to the quality of some of the evidence submitted, inconclusive results were not unexpected. A ground truth of elimination and comparison result of inconclusive was observed at a rate of 74%, while a ground truth of identification and comparison result of inconclusive was observed at a rate of 31%. Bullets (61.8%) were the main contributors to inconclusive conclusions; variables such as the assigned examiners, training program, examiner experience, and the intended complexity of the case did not significantly contribute to the results. The program demonstrates that the quality management system and firearms section procedures can obtain accurate and reliable results and provides examiners added confidence in court. Additionally, the program can be tailored to target specific research questions and provide opportunities for collaboration with other laboratories and researchers.

Exploring the use of machine learning for the assessment of skeletal fracture morphology and differentiation between impact mechanisms: A pilot study.

Analyzing and interpreting traumatic injuries is a fundamental aspect of routine forensic case work. As the human skeleton can be impacted through a combination of loading mechanisms and varying impact energies, the analysis and interpretation of skeletal trauma can be complex. Therefore, it is imperative that the reliability of techniques used for analysis are well-established. There is growing interest in machine learning (ML) in medicine (especially radiology) regarding the use of image classification (a subset of ML) to categorize and predict classes of medical images. Therefore, the feasibility of using image classification for skeletal trauma analysis should be explored for its benefits to forensic pathology and anthropology. The method explored in this paper examined the potential for machine learning, using three dimensional (3D) convolutional neural networks (CNNs), to assess whether morphological features of skeletal trauma to the femur can be used to differentiate between impact mechanisms within a forensic population. The objective of this study was to assess if morphological differences in femoral fractures seen in post-mortem-computed tomographic images (PMCT) could be categorized according to mechanism, specifically horizontal impacts resulting from pedestrian motor vehicle impacts (PMVIs) and vertical impact s resulting from high impact falls. Final model results indicated an accuracy between 69.95%-72.86% and 63.08%-66.24% validation. Although these results mean the method could not be practically used in its current form, as a proof of concept, there is potential for it to be developed as a tool to assist in classifying complex fracture states.

Providing a Forensic Expert Opinion on the "Degree of Force": Evidentiary Considerations.

Simple SummaryWhen giving evidence in court, forensic pathologists and anthropologists are often asked for their opinion on the amount, or degree of force required to cause a specific injury. Such ‘degree of force’ questions are considered difficult, if not impossible to answer due to many theoretical and practical issues. This paper explores these issues and provides a possible solution. First, the logical underpinnings of the question on the ‘degree of force’ are explored. Then the experimental research on ‘degree of force’ is reviewed and the limitations with applying this research to everyday forensic casework are discussed. In the second part of the paper, it is argued that these limitations do not, however, mean that a forensic pathologist or anthropologist cannot add anything of value to the discussion. The application of Bayes’ theorem helps to circumvent many of the problems. The final part of the paper is dedicated to a detailed discussion of how it can be applied to the issue of ‘degree of force’.Forensic pathologists and anthropologists are often asked in court for an opinion about the degree of force required to cause a specific injury. This paper examines and discusses the concept of ‘degree of force’ and why it is considered a pertinent issue in legal proceedings. This discussion identifies the implicit assumptions that often underpin questions about the ‘degree of force’. The current knowledge base for opinions on the degree of force is then provided by means of a literature review. A critical appraisal of this literature shows that much of the results from experimental research is of limited value in routine casework. An alternative approach to addressing the issue is provided through a discussion of the application of Bayes’ theorem, also called the likelihood ratio framework. It is argued that the use of this framework makes it possible for an expert to provide relevant and specific evidence, whilst maintaining the boundaries of their field of expertise.

Investigation of Mosaicism Detected in STR Typing

Short tandem repeats (STRs) are the most popular markers for human identification in forensics. These markers can be easily analyzed through a multiplex polymerase chain reaction and electrophoresis and provide high discrimination power. However, in STR analysis, several atypical phenomena can be observed such as allelic dropouts, drop-ins, or imbalance, which may be due to DNA polymerase slippage or DNA degradation effects. The observed atypical STR profiles can also provide information for mixed DNA samples or chromosomal abnormalities. In this study, we report a case of mosaicism detected in routine casework of paternity testing. Hair samples from a phenotypically normal male were tested, and the result presented a typical STR profile of a female for the amelogenin gene (XX). Through chromosome analysis using peripheral blood, it was found that 45,X/46,XY mosaicism resulted in the discrepancy between the genotype and the phenotype. In addition, the amount of Y chromosome detected was particularly low in hair compared to that in blood. This study shows that mosaicism can make interpretation difficult during STR analysis and suggests that sample types and repeated analysis should be considered even for routine STR testing.