Casework Scenarios Research Articles

Introduction to the Special Issue: Family Science Careers Through the Eyes of Theory

This manuscript is part of a special issue of Family Science Review entitled Family Science Careers Through the Eyes of Theory, edited by Raeann Hamon, Ph.D., CFLE. The authors of these deliberately unconventional manuscripts were asked to select and describe a career that a professional with a family science background might pursue. After outlining the professional role, authors reflected upon the family theories that most influence the way they approach their work and perform their professional duties. Authors briefly review the scholarly literature on selected family theories, provide case studies or work scenarios as illustrations of theory in action, and discuss the strengths and weaknesses of the theories in their unique professional contexts. The Special Issue articles are designed to be used individually or in combination, and feature articles about careers in early intervention, special education, family court, child life, and higher education.

DNA profiling in India: Addressing issues of sample preservation, databasing, marker selection, & statistical approaches

DNA technology is the gold standard with respect to the identification of individuals from biological evidence. The technology offers the convenience of a universally similar approach and methodology for analysis across the globe. However, the technology has not realised its full potential in India due to the lack of a DNA database and lacunae in sample collection and preservation from the scene of crime and victims (especially those of sexual assault). Further, statistical interpretation of DNA results is non-existent in the majority of cases. Though the latest technologies and developments in the field of DNA analysis are being adopted and implemented,very little has been enacted practically to improve optimise sample collection and preservation. This article discusses current casework scenarios that highlight the pitfalls and ambiguous areas in the field of DNA analysis, especially with respect DNA databases, sampling, andstatistical approaches to genetic data analysis. Possible solutions and mitigation measures are suggested.

Initial testing of an applicator prototype to facilitate forensic DNA recovery by tapelifting

ABSTRACT A tapelift used for DNA recovery can be prone to user contamination due to excessive handling when applying it to a surface and placing it into an extraction tube. Here, we present initial results from testing our newly developed applicator with tapelifts compared against the manual tapelift method. With subsequent testing of its performance across various surface types and casework scenarios, it is hoped that this applicator will revolutionize the way tapelifts are used to collect DNA at crime scenes.

From clean spaces to crime scenes: Exploring trace DNA recovery from titania-coated self-cleaning substrates

Titanium dioxide (titania, TiO2) is frequently used as a coating for a variety of self-cleaning products, such as antifogging vehicle mirrors, ceramic tiles, and glass windows because of its distinct physiochemical features. When exposed to light TiO2 causes photocatalytic decomposition of organic contaminants, potentially compromising DNA integrity. The impact of TiO2-coated commercial glasses, Bioclean® and SaniTise™, on trace DNA persistence, recovery, and profiling was investigated. DNA in saliva and touch samples deposited on self-cleaning glass slides exposed to indoor fluorescent light for up to seven days was more degraded than control samples indicating some degree of fluorescent light-induced photocatalytic activity of the self-cleaning surfaces. When exposed to sunlight, DNA yields from saliva and touch samples deposited on the titania-coated substrates decreased rapidly, with a corresponding increase in DNA degradation. After three days no DNA samples applied to self-cleaning glass and exposed to natural sunlight yielded STR profiles. These results suggest that the photocatalytic activation of TiO2 is the likely mechanism of action underlying the extreme DNA degradation on the Bioclean® and SaniTise™ glasses. Consequently, rapid sample collection and use may be warranted in casework scenarios involving TiO2-coated materials.

Interpretation and report writing in forensic comparisons of paint evidence: An interlaboratory exercise

This interlaboratory study evaluated a guide for interpreting and reporting trace evidence examinations. The online survey aimed to assess the examiners' interpretation of casework scenarios designed by a subject matter expert panel (SMEP), specifically for paint evidence. A pool of 30 scenarios was created, and 15 were assigned to each participant using multi-factor design to evaluate agreement among examiners on case sets with different conclusion ranges and difficulty levels. Exploratory data analysis and three generalized mixed-effects models were used to assess the data. From the 1267 responses received from 85 participants, approximately 93% of responses were consistent between participants and within the SMEP consensus and the next best category, while 73% agreed with the SMEP consensus that was considered the ground truth. Most disagreements were observed in worst-case scenarios created with intended higher difficulty and complex circumstances.The statistical models showed a strong positive relationship between the reported and expected conclusions, indicating that participants' findings align with the SMEP consensus. On the other hand, the exercise's difficulty level and participant's experience did not have a significant impact on the reported conclusions. However, the credible intervals for the probabilities of the different reported conclusions indicate that more experienced participants achieve greater consensus for a given exercise. The consensus reached among practitioners represents an advance in the trace community’s efforts to standardize reporting of results and opinions when following systematic criteria.

Examining the transfer of male DNA onto female underwear in simulated non sexual social interaction versus digital penetration to assist in the evaluation of results in casework scenarios

Experiments have been carried out by the UK and Ireland Association of Forensic Science Providers Body Fluid Forum (AFSP BFF) to determine the levels of male DNA, detected during Y-STR analysis, that may be expected on female underwear from non-sexual social interaction and digital penetration, versus non-sexual social interaction only. The data obtained strongly supports the existing assumptions made: whilst low levels of DNA may be inadvertently transferred to the inside surface of a female’s underwear during social interaction with a male, there is a low expectation of detecting a matching Y-STR profile to that male, which is suitable for statistical evaluation, unless he is a co-habitant of that female.

Survivability versus rate of recovery for skeletal elements in forensic anthropology.

Survivability, the ability of a skeletal element to withstand taphonomic processes, is often equated to recoverability, the probability that an element will be recovered in a forensic context, and further misused to infer the likelihood that a forensic anthropologist will recover a particular element at a scene. Consequently, researchers have utilized notions of survivability to infer that a skeletal element may be recovered when justifying the necessity of various research endeavors. This is problematic because the factors impacting survivability are not always applicable in a forensic context; the ability of a bone to survive taphonomic processes may not align with the likelihood of recovery. Empirical recovery rates are presented from two distinct contexts, with data derived from the Forensic Anthropology Data Bank based on cases performed by the late J. Lawrence Angel (1914-1986) and cases done by the University of Tennessee Knoxville (UTK). Recovery rates may be influenced by factors beyond survivability, though we do not investigate the many considerations that might explain recovery rate variation between datasets. Rather, these data exemplify the conceptual differences between notions of survivability and rates of recovery in actual casework scenarios. Thus, it is proposed that researchers consider documented rates of recovery when providing rationale for forensic anthropology research endeavors, in addition to citing a rationale that is based on inferences of survivability. This ensures that the theoretical framework of future forensic anthropology research stems, primarily, from the premise of practical application.

Lockdown labs: Pivoting to remote learning in forensic science higher education

Forensic Science training and education is reliant on the application of knowledge to casework scenarios and the development of key practical skills that provide a platform for career development in the field. The COVID-19 pandemic introduced a number of challenges to effectively deliver practical content online and remotely, whilst still meeting intended learning outcomes, accreditation requirements, and attaining a high level of student engagement and experience. The MSc Forensic Science programme featured in this study is a one-year degree programme with a strong emphasis on the practical elements of forensic science, and a diverse international student cohort. Therefore, the restrictions associated with the pandemic made it very difficult not only to plan the delivery of material but also to adapt the content itself for effective online and remote learning.By focusing on the intended learning outcomes, a number of innovative teaching practices were developed to successfully transition from face-to-face teaching to online and remote delivery. A range of online and practical resources were developed, including a laboratory home kit, demonstration videos, online practical technique simulations (produced by Learning Science), data analysis tasks, and interactive workshops and activities, all designed to consolidate student learning and build confidence, in preparation for such a time that on campus practical teaching could resume. The initial feedback received from these activities from both staff and students was extremely positive and the transition from classroom to online teaching was a success, as reflected in student attainment and later student feedback. Students reported that they had a better understanding of what was expected of them, including knowledge of protocols and techniques, and felt much more confident moving into the next stage of their learning development. Even though the practical laboratory sessions were the most significantly affected by the restrictions associated with the pandemic, and resulted in reduced interaction for the students, this was counteracted by virtual sessions and workshops, which gave students the opportunity to engage with each other and communicate their thoughts and opinions, ultimately building key presentation and group working skills.This case study will detail the pivot to remote learning, as well as critically evaluating the feedback from students and discussing the changes that are likely to be retained as longer-term teaching practices, versus those that were a necessary temporary addition or adjustment in response to the pandemic.

Latent fingermark detection using functionalised silicon oxide nanoparticles: Optimisation and comparison with cyanoacrylate fuming

Among the different types of nanoparticles (NPs) proposed for fingermark detection, silicon oxide nanoparticles (SiO2 NPs) are arguably the most promising due to their unique characteristics. In this study, carboxyl-functionalised SiO2 NPs doped with luminescent ruthenium complex—RuBpy-doped CES-SiO2 NPs—were further studied to investigate their effectiveness for latent fingermark detection. A modified version of the functionalised SiO2 NPs with a lower amount of surface functionalisation is proposed for improved fingermark detection effectiveness. A shaking incubator was also incorporated into the fingermark detection process to offer a more viable treatment approach in comparison to the previously published method. The shaking incubator offered a more robust application approach, as well as improved fingermark detection quality. To gain an insight into fingermark detection effectiveness relative to benchmark techniques, the performance of the optimised RuBpy-doped CES-SiO2 NPs was compared to that of a benchmark fingermark detection method—cyanoacrylate fuming (CAF) followed by luminescent dye staining. Relative fingermark detection effectiveness across the two techniques was evaluated via the treatment of 1724 fingermark specimens. It was concluded that, in general, the benchmark method provided superior detection results. It was evident that the SiO2 NPs are less affected by donor variability but are more dependent on substrate types. Such characteristics are encouraging as they could be favourable to practitioners in casework scenarios where the substrate is known but donor variability is obscure prior to fingermark processing. It should be noted that the overall effectiveness of the proposed NP-based technique will need to be improved before it could be considered for operational implementation.

The potential of collaborative learning as a tool for forensic students: Application to signature examination

Transferring theoretical knowledge to practical skills remains a big challenge in forensic science, especially in questioned documents. The examination of handwriting and signatures requires years of practice to develop the necessary skills. While students (and to some extent the general population) often have the impression that it is easy to differentiate handwriting from different persons, in practice, particularly when dealing with simulated signatures, there is a high risk of reaching a wrong conclusion when questioned document experts do not use a systematic approach and/or are not sufficiently experienced (see for example the famous French Dreyfus case). Thus, a novel teaching approach, based on collaborative learning, has been introduced in a theoretical handwriting class to improve the students’ theoretical knowledge, and additionally make them aware of the limitations of their practical skills and give them tools to improve them in their future practice. Through five activities, the students took the roles of victims, forgers, teachers and experts and created their own learning materials (i.e. signatures and mock casework). During those interactive activities, they learned to describe their signature’s characteristics, intra-variability and complexity, and thus evaluate their own signature’s vulnerability (as potential victims). They learned techniques to simulate signatures and detect the resulting forgeries’ characteristics (in the role of forgers). In the role of teachers, they prepared mock casework scenarios and gave feedback to their colleague’s examination of the produced material. As experts, they carried out signature examination as they would in a proficiency test and were exposed to the difficulties an actual expert may encounter in practice. The evaluation of this novel teaching scenario was very positive, as students learned more extensively the possibilities and limitations of signature comparison. They were more active and motivated in their learning experiences. The teaching team also had an improved experience. Some students complained of an increased workload and imprecise instructions. Improvements were tested and are discussed in this paper.

Validation of a streamlined RT-qPCR method for body fluid identification

Forensic DNA STR profiling provides information on the sub-source of DNA samples. However, other source information such as the type of body fluid from which a DNA profile is derived is required to better attribute a matching DNA profile to an individual and to provide activity level evidence. A range of biological molecules such as protein, mRNA and miRNA have been previously used for body fluid identification (BFID). However, many of the published options are complex and require multiple profiling pathways or multiple replicates to obtain interpretable data.We have developed a simplified workflow to deliver an RT-qPCR based system for identification of body fluids using mRNA. The process uses a modified DNA extraction protocol to optimise co-extraction of mRNA and DNA into the same sample eluate, avoiding the requirement for a specialised extraction protocol for mRNA. To simplify the subsequent analysis, we focus on binary tests for two body fluids only, which reflect common questions relevant to different casework scenarios, for example “Does this sample contain saliva or vaginal fluid?” This approach enables the development of smaller, simpler multiplexes using highly specific one-step RT-qPCR assays, designed not to be affected by the presence of genomic DNA. These RT-qPCR multiplexes provide a large dynamic range limiting the number of replicate amplifications required.Here we detail the validation of this streamlined BFID system for identification of saliva and vaginal fluid samples which are commonly encountered in investigations of sexual offences. The study included an assessment on a wide range of sample types obtained from consenting volunteers following sexual activity, providing a robust data set demonstrating the performance of the system.

Identification of post-blast explosive residues using direct-analysis-in-real-time and mass spectrometry (DART-MS)

Application of Direct-Analysis-in-Real-Time (DART) ionization with mass spectrometry (DART-MS) to identify homemade explosive (HME) residue recovered from genuine post-blast bomb fragments is presented. A variety of simulated improvised explosive devices (IEDs) were configured to replicate post-blast debris representative of materials encountered in real forensic casework scenarios. Peroxide-based HME was used as explosive filler: triacetone triperoxide (TATP), hexamethylene triperoxide diamine (HMTD) and methyl ethyl ketone peroxide (MEKP). Each IED was fired separately and the recovered fragments analyzed using full scan with high-resolution mass spectrometry. Fragments were analyzed directly and indirectly using cotton swabs and the target explosive was detected using either sampling technique. This work demonstrates the forensic validity of DART-MS to provide rapid and quality-assured identification of explosive residues from real post-blast IED fragments.

Identity informative SNP associations in the UK Biobank

Single nucleotide polymorphisms (SNPs) are amenable to genotyping DNA from degraded, inhibited, and/or ancient substrates due to their relatively small amplicon size. Though they have clear advantages over traditional short tandem repeat (STR) typing for specific casework scenarios, the advances in massively parallel sequencing (MPS) have drastically increased the utility of this marker type. The biallelic nature of SNPs makes them individually less informative than STRs due to limited heterozygosity; however, in sufficiently large multiplexes, identity informative SNPs (iiSNPs) may produce combined random match probabilities comparable to STR typing. Multiple MPS library preparation kits now include iiSNPs and similar to STRs, these loci have been rigorously characterized during multiplex development. The relative accessibility of genome-wide association study (GWAS) summary statistics enables re-investigation of forensically relevant targets in high-quality datasets. Here, 4085 GWASs from the UK Biobank European datasets (UKB; 787 ≤ N ≤ 361,194) were mined for iiSNPs typed by the ForenSeq DNA Signature Prep Kit (Verogen). Seven iiSNPs had genome-wide association (p ≤ 5 × 10−8) with 17 phenotypes in UKB Europeans. Most notably, these relationships involve two outwardly visible characteristics: standing height (rs907100; β = 0.011, p = 1.35 × 10-10) and hair/balding patterns (rs2399332; β = −0.009, p = 3.83 × 10−8). The remaining associations involve red blood cell characteristics and measures of lung function. Though these traits are highly polygenic and the individual SNP effects described here have been refuted empirically, we describe the importance and ease of exploring high-quality, freely accessible data to continuously and robustly characterize new and existing forensically relevant loci.

The forensic analysis of office paper using oxygen Isotope Ratio Mass Spectrometry, part 2: Characterising the source materials and the effect of production and usage on the δ18O values of cellulose and paper

For casework applications, understanding the source processes used to create a material and the effects of those sources on the results obtained by Isotope Ratio Mass Spectrometry (IRMS) of a bulk material is important. Likewise, understanding the effect of environment, home/office printing processes and some forensic testing in at least a basic context, ensures that in casework, enough information on the effects of these variables is available during comparison and interpretation.In this study, which focuses on oxygen isotopic abundance measurements, both fractionation and mixing effects were observed within the pulping and production process. Also observed in the carbon isotopic experiments, sampling that included toner changed the measured isotopic abundance values of the paper and should be avoided in casework. Inkjet printing processes were not shown to have an effect on the paper oxygen abundance values. Samples that were treated for fingerprints using 1,2-Indandione-Zn prior to sampling showed the greatest risk for misinterpretation of whether two samples had originated from the same source. While this study provides a good basis and understanding of the effects of a range of factors on document paper oxygen isotope values, further testing for a range of specific casework scenarios is required and should be undertaken on a case by case basis as the need arises.

A Validation Study of Bullet and Cartridge Case Comparisons Using Samples Representative of Actual Casework.

The foundation of firearm and tool mark identification is that no two tools should produce the same microscopic marks on two separate objects that they would be inaccurately or wrongly identified. Studies addressing the validity of identification infrequently employ tests that mirror realistic casework scenarios. This study attempted to do so using a double-blind process, reducing test-taking bias. Test kits including bullets and cartridge cases but not the associated firearms were completed by 31 analysts from 22 agencies. Analysis of the results demonstrated an overall error rate of 0.303%, sensitivity of 85.2%, and specificity of 86.8%. Variability in performance across examiners is addressed, and the effect of examiners' years of experience on identification accuracy is explored. Finally, the article discusses the importance of studies using realistic case work scenarios when validating the field's performance and in providing courts with usable indicators of the accuracy of firearm and tool mark identification.

Simulating forensic casework scenarios in experimental studies: The generation of footwear marks in blood

A study was designed to investigate the effects of external variables, including blood type, flooring surface, footwear tread depth and blood dryness, on the appearance of blood-based footwear marks, with particular reference to simulating a specific casework scenario. Results showed that footwear marks left in human blood tended to be of greater quality than those in equine blood, highlighting a potential issue in applying data generated with equine blood to human bloodstains in casework. Footwear tread effects were also dependent on blood type, but the type of flooring surface did not affect the appearance of the mark. Under some conditions, as the blood dried, the amount of detail retained from footwear contact decreased. These results provide the beginnings of an empirical evidence base to allow a more accurate interpretation of blood-based footwear marks in forensic casework. When applied to a disputed bloodstain in a specific case, these results also demonstrate the importance of such experiments in narrowing the range of explanations possible in the interpretation of forensic evidence.

DNA transfer by examination tools – a risk for forensic casework?

The introduction of profiling systems with increased sensitivity has led to a concurrent increase in the risk of detecting contaminating DNA in forensic casework. To evaluate the contamination risk of tools used during exhibit examination we have assessed the occurrence and level of DNA transferred between mock casework exhibits, comprised of cotton or glass substrates, and high-risk vectors (scissors, forceps, and gloves). The subsequent impact of such transfer in the profiling of a target sample was also investigated. Dried blood or touch DNA, deposited on the primary substrate, was transferred via the vector to the secondary substrate, which was either DNA-free or contained a target sample (dried blood or touch DNA). Pairwise combinations of both heavy and light contact were applied by each vector in order to simulate various levels of contamination.The transfer of dried blood to DNA-free cotton was observed for all vectors and transfer scenarios, with transfer substantially lower when glass was the substrate. Overall touch DNA transferred less efficiently, with significantly lower transfer rates than blood when transferred to DNA-free cotton; the greatest transfer of touch DNA occurred between cotton and glass substrates. In the presence of a target sample, the detectability of transferred DNA decreased due to the presence of background DNA. Transfer had no impact on the detectability of the target profile, however, in casework scenarios where the suspect profiles are not known, profile interpretation becomes complicated by the addition of contaminating alleles and the probative value of the evidence may be affected. The results of this study reiterate the need for examiners to adhere to stringent laboratory cleaning protocols, particularly in the interest of contamination minimisation, and to reduce the handling of items to prevent intra-item transfer.

Investigation of Isotopic Linkages between Precursor Materials and the Improvised High Explosive Product Hexamethylene Triperoxide Diamine

The results of isotope ratio mass spectrometry (IRMS) on hexamethylene triperoxide diamine (HMTD) and its precursor hexamethylenetetramine (hexamine) is presented. HMTD was prepared from hexamine using several different sources of hexamine under both controlled laboratory conditions and in field experiments that represent the less controlled conditions that are likely to be observed in forensic casework scenarios. Precursor and product carbon isotope δ values consistently fit a linear relationship regardless of precursor or conditions. The magnitude of the isotope fractionation observed is affected by the efficiency of the reaction, with greater yielding reactions giving rise to HMTD with δ values more similar to the precursor material than lower yielding reactions. Nitrogen isotope δ values comparing precursor with product show some linearity when the reaction conditions are carefully controlled; however, results indicate a poor fit with linearity when synthesis conditions are more variable. Despite the greater variation, the HMTD product consistently has a more positive δ value compared with the hexamine precursor. The results observed from these experiments suggest hexamine reacts to form HMTD in a 1:1 ratio. Having prepared multiple HMTD samples from various precursors using a range of experimental conditions, we have observed results that may be useful in forensic investigations of improvised explosive materials.

Impact of relevant variables on the transfer of biological substances

There is a paucity of data on the relative amounts of DNA containing material that is likely to be transferred given specific casework scenarios that incorporate multiple transfer steps. Availability and application of such data could be helpful in estimating the probability of a given set of circumstances actually occurring. Here we utilise data on transfer percentages, given knowledge of specific variables (type of biological substance, level of moisture of the biological substance, the substrate on which the sample is located, the substrate with which it comes into contact, and the manner of contact), as determined by Goray et al. [1,2] to extrapolate the amount of DNA expected to be retrieved from a targeted sample area, under particular multi-transfer step scenarios. We demonstrate that, in many scenarios incorporating multiple transfer steps, unrealistically large amounts of biological material would need to be present at source to generate a detectable level of DNA from the targeted crime scene surface. These findings will assist in comparing the likelihood of postulated alternative crime scenarios involving DNA transfer, at the investigation stage and/or during court proceedings.