Current state and progress of research on forensic biomechanics in China

Forensic biomechanics gradually has become a significant component of forensic science. Forensic biomechanics is evidence-based science that applies biomechanical principles and methods to forensic practice, which has constituted one of the most potential research areas. In this review, we introduce how finite element techniques can be used to simulate forensic cases, how injury criteria and injury scales can be used to describe injury severity, and how tests of postmortem human subjects and dummy can be used to provide essential validation data. This review also describes research progress and new applications of forensic biomechanics in China.

Key points

• The review shows the main research progress and new applications of forensic biomechanics in China.
• The review introduces eight cases about the application of forensic biomechanics, including the multiple rigid body reconstruction, the finite element applications, study of mechanical properties, traffic crash reconstruction based on multiple techniques and analysis of morphomechanical mechanism about blood dispersal.
• Though forensic biomechanics has a great advantage for the evaluation of injury mechanisms, it still has some uncertainties owing to the uniqueness of the human anatomy, the complexity of biological materials, and the uncertainty of injury-causing circumstances.

     

DNA Barcoding Identifies all Immature Life Stages of a Forensically Important Flesh Fly (Diptera: Sarcophagidae)

Carrion‐breeding insects, such as flesh flies (Diptera: Sarcophagidae), can be used as evidence in forensic investigations. Despite their considerable forensic potential, their use has been limited because morphological species identification, at any life stage, is very challenging. This study investigated whether DNA could be extracted and cytochrome oxidase subunit I (COI) barcode sequences obtained for molecular identification of each immature life stage of the forensically important Australian flesh fly, Sarcophaga (Sarcorohdendorfia) impatiens (Walker). Genomic DNA extracts were prepared from all larval instars and puparia. Amplification of the barcoding region was successful from all extracts, but puparia amplicons were weak. All sequences were identified as S. impatiens with 99.95% confidence using the Barcoding of Life Database (BOLD). Importantly, crop removal was necessary to eliminate PCR inhibition for specimens from late second and early third instars. Similar results are expected for immatures of other carrion‐breeding species, enhancing the use of evidence from immature flies in forensic investigations.     

Quantitative evaluation of the results of digital forensic investigations: a review of progress

Unlike conventional forensics, digital forensics does not at present generally quantify the results of its investigations. It is suggested that digital forensics should aim to catch up with other forensic disciplines by using Bayesian and other numerical methodologies to quantify its investigations’ results. Assessing the plausibility of alternative hypotheses (or propositions, or claims) which explain how recovered digital evidence came to exist on a device could assist both the prosecution and the defence sides in criminal proceedings: helping the prosecution to decide whether to proceed to trial and helping defence lawyers to advise a defendant how to plead. This paper reviews some numerical approaches to the goal of quantifying the relative weights of individual items of digital evidence and the plausibility of hypotheses based on that evidence. The potential advantages enabling the construction of cost-effective digital forensic triage schemas are also outlined.

Key points

• The absence of quantified results from digital forensic investigations, unlike those of conventional forensics, is highlighted.
• A number of approaches towards quantitative evaluation of the results of digital forensic investigations are reviewed.
• The significant potential benefits accruing from such approaches are discussed.

     

Hydrocarbon and Fatty Acid Composition from Blowfly Eggs Represents a Potential Complementary Taxonomic Tool of Forensic Importance,

One of the most important contributions of forensic entomology is to assist criminal expertise to determine the postmortem interval, which depends on the duration of the immature stages of insects of forensic interest. On the other hand, the time of development of the different stages varies according to the species; therefore, its identification is essential. Currently, few studies have investigated the use of cuticular hydrocarbons, and none regarding fatty acids, as complementary taxonomic tools to expedite species identification. Therefore, we evaluated whether cuticular hydrocarbons together with fatty acids of eggs of flies of the family Calliphoridae, main group of forensic interest, can be used to distinguish species. The analyses were performed by chromatographic techniques. The results show that there are significant differences between the composition of cuticular hydrocarbons and fatty acids between species and, therefore, they can be used to provide a complementary taxonomic tool to expedite the forensic expertise.     

Forensic isoscapes based on intra-individual temporal variation of δ18O and 206Pb/207Pb in human teeth

Isotopic signatures used in the georeferencing of human remains are largely fixed by spatially distinct geologic and environmental processes. However, location-dependent temporal changes in these isotope ratios should also be considered when determining an individual’s provenance and/or trajectory. Distributions of the relevant isotopes can be impacted by predictable external factors such as climate change, delocalisation of food and water sources and changes in sources and uses of metals. Using Multi-Collector Inductively-Coupled Plasma Mass Spectrometer (MC-ICP-MS) analyses of ²⁰⁶Pb/²⁰⁷Pb in tooth enamel and dentin from a population of 21 ± 1-year-old individuals born circa 1984 and isotope ratio mass spectrometry (IRMS) of δ¹⁸O in their enamel, we examined the expected influence of some of these factors. The resulting adjustments to the geographic distribution of isotope ratios (isoscapes) found in tooth enamel and dentin may contain additional useful information for forensic identification, but the shifts in values can also impact the uncertainty and usefulness of identifications if they are not taken into account.

KEY POINTS

• Isoscapes of ²⁰⁶Pb/²⁰⁷Pb and δ¹⁸O used for geolocation are not static.
• Within a few years, the enamel and dentin of a person may exhibit measurable differences in ²⁰⁶Pb/²⁰⁷Pb even without changing locations.
• Changes in climatic patterns tied to rising temperatures are more significant than the direct effect of increasing temperature on δ¹⁸O fixed in tooth bioapatite.
• Third molar (M3) enamel mineralisation includes material incorporated from before formal amelogenesis takes place.

     

Probative Value of Absolute and Relative Judgments in Eyewitness Identification

It is well-accepted that eyewitness identification decisions based on relative judgments are less accurate than identification decisions based on absolute judgments. However, the theoretical foundation for this view has not been established. In this study relative and absolute judgments were compared through simulations of the WITNESS model (Clark, Appl Cogn Psychol 17:629–654, 2003) to address the question: Do suspect identifications based on absolute judgments have higher probative value than suspect identifications based on relative judgments? Simulations of the WITNESS model showed a consistent advantage for absolute judgments over relative judgments for suspect-matched lineups. However, simulations of same-foils lineups showed a complex interaction based on the accuracy of memory and the similarity relationships among lineup members.     

A review of experimental design in forensic taphonomy: moving towards forensic realism

Forensic taphonomy as a discipline requires standardization to satisfy Daubert criteria for scientific data to be admissible in court. In response, there has been a shift towards quantification of methodology and estimating the postmortem interval. Despite these advances, there are still biases and limitations within the discipline not explicitly addressed in the early stages of experimental design nor in final published works. In this article, unresolved debates with respect to the conductance and reporting of forensic taphonomic research are reviewed, beginning with the nature of experimental cadavers, human or animal analogues and their body size, and second, the forensic realism of experimental setups, specifically with respect to caging, clothing and number of carcases. Pigs, albeit imperfect, are a good model to gain a general idea of the trends that may be seen in humans in subsequent validation studies in facilities where human donors are available. To date, there is no consensus among taphonomists on the extent of the effect that body mass has on decomposition progression. More research is required with both human cadavers and non-human analogues that builds on our current knowledge of forensic taphonomy to answer these nagging questions. This will enable the discipline to make the reliable assumption that pigs and donor decomposition data can be applied to homicide cases. A suite of experimental design aspects is suggested to ensure systematic and standardized data collection across different biogeoclimatic circumstances to identify and quantify the effects of potential confounding variables. Such studies in multiple, varied biogeographic circumstances with standardized protocols, equipment and carrion will facilitate independent global validation of patterns. These factors are reviewed to show the need for adjustments in experimental design to ensure relevance and applicability of data within locally realistic forensic situations. The initiation of a global decomposition data network for forensic taphonomists is recommended.

Key points

• Pigs are a valuable, albeit imperfect, proxy for human decomposition studies.
• There are few or conflicting data on effects of carcase size, carrion ecology, exclusion cages and scavengers.
• We recommend single, clothed, uncaged carcases for baseline research to reflect regionally specific forensic casework.

     

Dental identification by comparison of antemortem and postmortem dental radiographs: influence of operator qualifications and cognitive bias

Dental forensic identifications based on comparison of antemortem and postmortem radiographs provide effective and reliable evidence. There are no standardized procedures for assessing similarities between different types of dental radiographs (e.g. orthopantomograms, bitewings, and periapical radiographs), and the operator's subjective judgment can considerably affect identification. The purpose of this study is to evaluate the potential influence of experts' qualifications, training, and cognitive bias on the accuracy of identification. Seventy-eight differently qualified and experienced experts underwent an identification test. The expert sample was composed of 10 specialists in emergency care (ER), 10 specialists in legal medicine (ML), 20 pregraduate dental students (STU), 12 dentists (DENT), 20 dentists educated in forensic odontology (DENT-TRA), and 6 experienced forensic odontologists (FOR). The simulated cases required participants to assess the possible matching of 42 postmortem intraoral radiographs with 16 antemortem panoramic radiographs. Accuracy and specificity for the different operator groups were as follows: ER, 0.76-0.70; ML, 0.76-0.88; STU, 0.89-0.82; DENT, 0.87-0.97; DENT-TRA, 0.88-0.92; and FOR, 0.97-1. As evidenced by high rates of accuracy and repeatability, the most experienced forensic odontologist consistently outperformed operators less or differently educated and trained, especially for difficult cases. In our sample, the dentists who received additional education in forensic odontology did not necessarily perform better than dentists who had not received this additional education. Some cognitive bias, mainly the so-called observer effect, emerged as a possible source of outcome variability among the operator groups.     

Development of a nanoplate-based digital PCR assay for species identification with mixture deconvolution

In crime scenes, not all biological stains are human in origin. Some exhibits can be from pets living on the premises or from animal products used in food consumption. In addition, it could be necessary to test animal carcasses for other forensic purposes. Often such stains can include mixtures involving humans or other species. Thus, identifying and deconvoluting mixtures of species commonly found in and around a household can be crucial in forensic casework. Different molecular techniques have been employed for species identification such as immunoprecipitation, qPCR, and DNA sequencing.In this project, a nanoplate-based digital PCR assay for species identification was developed, targeting Homo sapiens, canine, feline, bovine swine, pisces, and gallus in two multiplexes. An internal positive control was included in the design. The assay is simple, rapid, and can determine a wide variety of different vertebrates from biological exhibits, as well as in mixtures. Because the assay utilizes digital PCR, the procedure shows sensitivity down to a few copies, even in the presence of larger amounts of a major contributor, making the assay particularly useful in mixture deconvolution. Overall, this assay presents the forensic community with a novel application in which digital PCR can provide a sensitive and specific determination of species.     

Identifying forensically relevant urban scavengers in Johannesburg,South Africa

Unidentified human remains are frequently recovered in urban environments in South Africa, which undergo forensic (medico-legal) investigations. These remains often exhibit animal scavenging modifications and are frequently scattered by animals. This impacts the collection and forensic analysis of the remains. This study aimed to identify scavenging animals present in two urban environments in Johannesburg, South Africa, and describe their scavenging and scattering behaviours. Six pig carcasses (Sus scrofa domesticus) (30–80 kg) were placed in a veldt in Johannesburg and in an abandoned building complex. Motion-activated cameras recorded the scavenging activities. Scavenger species were identified and their behaviours, scattering pattern, and scavenging bone modifications were described. Slender mongooses (Galerella sanguinea) were the most prolific veldt scavengers. They scattered remains to a maximum distance of 10.5 m in two directions: north and southeast. These mongooses scavenged during the advanced and dry decomposition stages. Gnawing on the angle of the mandible - with multiple parallel scores on the flat surfaces and the angle margin having a stepped appearance - may be a distinguishing scavenging modification feature of the slender mongoose. Hadeda ibis (Bostrychia hagedash) were the only scavengers recorded scavenging on the intestines of a pig carcass in the abandoned building complex. They favoured colonizing insects and created multiple, large holes in the skin and removed the lips to access the insects. The described scavenging behaviours will assist in the reconstruction of postmortem events in forensic cases and the location and collection of scattered remains in Southern Africa.     

The 4 Ds of Forensic Mental Health Assessments of Personal Injury

The field of psychiatric/psychological injury and law concerns tort and other legal claims for injuries sustained in events at issue, such as in motor vehicle accidents (MVAs), worker compensation, or the veteran affairs (VA). The 4 Ds refer to the requirement that legal action in these types of cases can proceed when there is a duty, the duty has been discharged with dereliction, the resultant act has caused directly tortious harm, and damages are applicable. In contrast, the related 4 Cs refer to the conditions of effective forensic testimony. The principles of forensic mental health assessment (FMHA; Heilbrun et al., 2009) underscore the scientific requirements in forensic assessments, as do the American Psychological Association’s (APA, 2013) forensic specialty guidelines. For example, Brodsky’s maxims for effective work in court (Brodsky & Gutheil, 2016) cover a broad spectrum of ethical and practice guidelines for the profession. Similarly, Young (2016 a, b, c) has specified the parameters of admissible evidence in court, functioning ethically for the court, and the need to be comprehensive, scientifically informed, and impartial in forensic mental health assessments. All these sources lead to an integrated set of the principles for effective and ethical practice in the forensic arena of mental health work, referred here as the 4 Ds for the field of psychiatric/psychological injury and law. These revised 4 D principles involve Dignity, Distance, Data, and Determinations.     

Lessons learned from inter-laboratory studies of carbon isotope analysis of honey

Forensic application of carbon isotope ratio measurements of honey and honey protein to investigate the degree of adulteration with high fructose corn syrup or other C₄ plant sugars is well established. These measurements must use methods that exhibit suitable performance criteria, particularly with regard to measurement uncertainty and traceability – low levels of adulteration can only be detected by methods that result in suitably small measurement uncertainties such that differences of 1‰ or less can be reliably detected. Inter-laboratory exercises are invaluable to assess the state-of-the art of measurement capabilities of laboratories necessary to achieve such performance criteria. National and designated metrology institutes from a number of countries recently participated in an inter-laboratory assessment (CCQM-K140) of stable carbon isotope ratio determination of bulk honey. The same sample material was distributed to a number of forensic isotope analysis laboratories that could not participate directly in the metrological comparison. The results from these studies have demonstrated that the majority of participants provided isotope delta values with acceptable performance metrics; that all participants ensured traceability of their results; and that where measurement uncertainties were reported; these were fit-for-purpose. A number of the forensic laboratories only reported precision rather than full estimates of measurement uncertainty and this was the major cause of the few instances of questionable performance metrics. Reporting of standard deviations in place of measurement uncertainties is common practice outside metrology institutes and the implications for interpretations of small differences in isotopic compositions are discussed. The results have also highlighted a number of considerations that are useful for organisers of similar inter-laboratory studies in the future.     

Entomological identification of the post-mortem colonization of wolf cadavers in different decomposition stages

Human-driven biodiversity loss is progressively becoming a problem with dramatic consequences for the conservation of vital ecosystems. The increasing number of illegal killings of the grey wolf (Canis lupus, Linnaeus, 1758), a threatened species, displays the need for investigation and prosecution of such offences. Forensic entomology makes use of the knowledge about necrophagous insects to estimate a minimum time-since-death interval of the deceased person or animal, which can give important information on a possible perpetrator. The cadaver fauna along five decomposition stages of wolves in Germany was investigated in the period 2014–2021. The insects from 70 wolf cadavers, originating from all over Germany, were provided by the Leibniz Institute for Zoo and Wildlife Research Berlin. The accumulated degree day (ADD) model was applied for the post-mortem interval estimation on wolf cadavers for the first time. A total of 20 coleopteran species and 14 different dipteran species were discovered and identified. Almost 99 % of all insect specimens were from the order of Diptera, and beetles (Coleoptera) accounted for only 1 % of the cadaver fauna. The blowflies (Calliphoridae) are of particular importance for forensic issues, accounting for about 66 % of all families. Carrion beetles (Silphidae) were found as the second most abundant family (about 21 %). In addition, combining all cases, a steadily increasing insect species richness S was detected from early decay to advanced decay (fresh S = 8; bloated S = 12; active decay S = 21; advanced decay S = 34). In the following remains stage, the species number decreased again (S = 24). However, no significant difference in the number of species was found between the stages of decay when the cases were considered individually. The temporal pattern of insect appearance was found to be congruent with those of previous studies. Furthermore, a time of death was determined for each case and compared to the pathologist's estimates. This study provides insights into the arthropod fauna of wolf remains for the first time, applies the ADD-Model for post-mortem interval estimation, and discusses the suitability of forensic entomology for wildlife death investigations.     

Ear identification: a pilot study

Although several papers have recently been devoted to establishing the validity of identification using the ear, this part of the human body still remains underexploited in forensic science. The perfect overlap of two images of the same ear is not really possible, but photographs of the ears as a reliable means of inferring the identity of an individual are poorly treated in the literature. In this study, we illustrate a simple, reproducible method, which divides the photograph of an ear into four parts-helix, antihelix, concha, and lobe-by means of a suitable grid of four straight lines. Although the division does not follow exact anatomical features, their edges do join anatomical points which are more easily identifiable. Measurement of certain areas of these parts can be combined to produce a code allowing personal identification. This method produces false-positive identifications of <0.2%. Last, the repeatability and reproducibility aspects of the method are tested.     

The reliability of digitized radiographs for dental identification: a Web-based study

In the era of Daubert and other judicial rulings pertaining to the acceptability of forensic evidence, it is increasingly important that experts are able to testify that their methods have been scientifically tested and that error rates and other factors relating to reliability have been published. The purpose of this study was to determine the reliability of digitized radiographic comparisons for the purposes of dental identification. Participants with various forensic backgrounds and experience levels were passively recruited to the website. Ten forensic identification cases composed of antemortem and postmortem dental radiographs were supplied to examiners using a bespoke website. Participants responded to the cases on two occasions after a one-month washout interval using the ABFO conclusion levels for forensic identifications. A total of 115 first attempts and 87 matched second attempts were received. Of the total responses, 72% were dentally trained respondents who had completed at least one forensic identification case; of these, 38% were experienced forensic dentists who had completed more than 25 identifications. Data relating to accuracy, intra- and inter-examiner agreement, and the effect of case difficulty are presented. Mean accuracy was 85.5% for all cases, with the experienced forensic dentists obtaining a 91% success rate. The inter-examiner agreement on the negative identification cases was classified as poor. The data suggest that dental identifications resulting from the comparison of postmortem and antemortem radiographs are valid, accurate, and reliable when undertaken by experienced odontologists.     

Setting the Record Straight: Comment on Gurley,Piechowski, Sheehan,and Gray (2014) on the Admissibility of the Rorschach Performance Assessment System (R-PAS) in Court

Gurley et al. (Psychological Injury and Law 7:9–17, 2014) express reservations about the admissibility of testimony based on the Rorschach Performance Assessment System (R-PAS) in court. They question whether there is sufficient evidentiary foundation in the underlying psychometrics and adequate general acceptance among psychologists for R-PAS-based testimony to meet either the Daubert or Frye criteria for admissibility and also raise doubts about how well it meets the criteria for the use of forensic tests proposed by Heilbrun (Law and Human Behavior 16:257–272, 1992). This invited comment addresses their concerns about the admissibility of R-PAS-based testimony and corrects some erroneous statements about the psychometrics of R-PAS and the pertinent empirical literature. Gurley et al. characterize R-PAS as being in competition with the established Comprehensive System (CS; Exner 2003), though we clarify that it is actually an evolutionary development from the CS and designed to be a replacement for it. We also point out how their conclusion that R-PAS-based forensic testimony may be hazardous or premature is based on an insufficient familiarity with the R-PAS scientific and professional literature, a misinterpretation of the Frye and Daubert evidentiary standards, and a mischaracterization of several of Heilbrun’s (Law and Human Behavior 16:257–272, 1992) criteria for the use of tests in forensic testimony.     

Forensic DNA laboratory automation – Principles and guidelines

There is a lack of clear guidelines for project managers, laboratory managers and forensic scientists on strategies for the automation of forensic DNA laboratory processes and operational implementation of new technologies. This is reflected in the failure rate of projects in the forensic DNA testing environment. We present a set of guidelines and concepts important for forensic laboratory automation. Some case studies from past projects are presented. These consist of partial (or modular) automation (n = 2) and full automated robotically integrated systems (n = 2).Technology Management principles and concepts are crucial to prevent failure of projects, e.g. early adoption of untried technologies, and organizational factors. The future of laboratory automation is modular until such time as new discontinuous technologies will replace the need of the traditional manual laboratory configuration in totality.     

Impact of plastic wrapping on carcass decomposition and arthropod colonisation in northern Africa during spring

The effect of plastic wrapping on decomposition rate and carrion fauna of rabbits (Oryctolagus cuniculus L.) was examined in spring in a semi-urban area in North Algeria. All decomposition stages were observed in all carcasses, with the same durations in the control but different durations in the wrapped carcasses. Decomposition of the carcasses in the plastic wrapping was significantly slower than that of the exposed ones. A total of 12,516 specimens, belonging to 36 families and 69 species, were morphologically identified. Thirteen species of forensic relevance were also identified at the molecular level using the cytochrome c oxidase I (COI) barcode region, and the sequences were submitted to online databases. Wrapping had a significant effect on species composition (χ² = 569.269, df = 55, p < 0.001). Higher species richness, abundance, and diversity were found in the control group. No significant difference in species abundance was observed between the treatments. The plastic wrap did not influence the accessibility of carcasses to insects, nor did it delay the arrival of necrophagous flies. This study provides basic information on the decomposition and arthropod colonisation of wrapped remains and contributes to the literature on North African carrion fauna.