Scientific integrity in the forensic sciences: Consumerism,conflicts of interest,and transparency

The goal of this paper is to discuss scientific integrity, consumerism, conflicts of interest, and transparency within the context of forensic science. Forensic scientists play crucial roles within the legal system and are constantly under various pressures when performing analytical work, generating reports based on their analyses, or testifying to the content of these reports. Maintaining the scientific integrity of these actions is paramount to supporting a functional legal system and the practice of good science. Our goal is to discuss the importance of scientific integrity as well as the factors it may compromise, so that forensic practitioners may be better equipped to recognize and avoid conflicts of interest when they arise. In this discussion we define terms, concepts, and professional relationships as well as present three case studies to contextualize these ideas.     

Investigation of infinite focus microscopy for the determination of the association of blood with fingermarks

The determination of the type of deposition mechanism of blood within fingermarks at the scene of violent crimes is of great importance for the reconstruction of the bloodshed dynamics. However, to date, evaluation still relies on the subjective visual examination of experts. Practitioners encounter three types of scenarios in which blood may be found in fingermarks and they refer to the following three deposition mechanisms: (i) blood marks, originating from a bloodied fingertip; (ii) marks in blood, originating from a clean fingertip contacting a blood contaminated surface; (iii) coincidental deposition mechanisms, originating from a clean fingertip contacting a clean surface, leaving a latent fingermark, and subsequent contamination with blood. The authors hypothesised that, due to differences in distribution of blood in the furrows and on the ridges, the height of blood depositions on the ridges and furrows (and their relative proportions), will differ significantly across the three depositions mechanisms. A second hypothesis was made that the differences would be significant and consistent enough to exploit their measurement as a quantitative and objective way to differentiate the deposition mechanisms.In recent years, infinite focus microscopy (IFM) has been developed, allowing for the computational generation of a 3D image of the topology of a sample via acquisition of images on multiple focal planes. On these bases, it was finally hypothesised that the application of this technique would allow the distinction of deposition mechanisms (i) to (iii). A set of preliminary experiments were designed to test whether IFM was “fit for purpose” and, subsequently, to test if any of the three deposition mechanisms scenarios could be differentiated. Though IFM enabled the analysis of tape lifted samples with some success, for samples produced and analysed directly on the surface of deposition, the results show that the measurements from any scenario will be highly dependent on the original surface of deposition (both in terms of its nature and of the variable exposure to environment); as crime scenes exhibit a wide range of possible relevant surfaces of deposition, the technique showed to not have the desired wide appeal for inclusion into a standardised set of protocols within a routine crime scene workflow.     

Exposing latent fingermarks on problematic metal surfaces using time of flight secondary ion mass spectroscopy

Fingermarks are a key form of physical evidence for identifying persons of interest and linking them to the scene of a crime. Visualising latent (hidden) fingermarks can be difficult and the correct choice of techniques is essential to develop and preserve any fingermarks or other (e.g. DNA) evidence that might be present. Metal surfaces (stainless steel in particular) have proven to be challenging substrates from which to reliably obtain fingermarks. This is a great cause for concern among police forces around the globe as many of the firearms, knives and other metal weapons used in violent crime are potentially valuable sources of fingermark evidence. In this study, a highly sensitive and non-destructive surface science technique called time of flight secondary ion mass spectroscopy (ToF-SIMS) was used to image fingermarks on metal surfaces. This technique was compared to a conventional superglue based fuming technique that was accompanied by a series of contrast enhancing dyes (basic yellow 40 (BY40), crystal violet (CV) and sudan black (SB)) on three different metal surfaces. The conventional techniques showed little to no evidence of fingermarks being present on the metal surfaces after a few days. However, ToF-SIMS revealed fingermarks on the same and similar substrates with an exceptional level of detail. The ToF-SIMS images demonstrated clear ridge definition as well as detail about sweat pore position and shape. All structures were found to persist for over 26?days after deposition when the samples were stored under ambient conditions.     

The effect of antifreeze (ethylene glycol) on the survival and the life cycle of two species of necrophagous blowflies (Diptera: Calliphoridae)

Entomotoxicology involves the analysis of the presence and the effects of toxicological substances in necrophagous insects. Results obtained by entomotoxicological studies may assist in the investigation of both the causes and the time of death of humans and animals. Ethylene glycol (EG) is easy to purchase, sweet and extremely toxic. It may be consumed accidentally or purposefully, in an attempt to cause death for suicidal or homicidal intent. Several cases report fatalities of humans and animals. The present study is the first to examine the effects of EG on the survival, developmental rate and morphology of two blowfly species, (Diptera: Calliphoridae) typically found on corpses and carcasses: Lucilia sericata (Meigen) and L. cuprina (Wiedemann). Both species were reared on substrates (beef liver) spiked with three different concentrations of EG that could cause death in either a human or cat: 1/2LD₅₀ (T1), LD₅₀ (T2), 2LD₅₀ (T3), in addition to a control treatment (C) with no EG.Results of this research show that: a) both species are unable to survive if reared on a food substrate spiked with the highest concentration of EG (T3), while lower and medium concentrations (T1, T2) affect, but not prevent, the survival and the completion of the life cycle of such species; b) adults of L. sericata eclose only in C and T1, while adults of L. cuprina in both C, T1, T2; however, c) the developmental time of both species reared in T1 and T2 is statistically slower than the control; d) the body length of the immatures of both of the species reared in T1 and T2 is statistically smaller than the control.     

Choice of population database for forensic DNA profile analysis

When evaluating the weight of evidence (WoE) for an individual to be a contributor to a DNA sample, an allele frequency database is required. The allele frequencies are needed to inform about genotype probabilities for unknown contributors of DNA to the sample. Typically databases are available from several populations, and a common practice is to evaluate the WoE using each available database for each unknown contributor. Often the most conservative WoE (most favourable to the defence) is the one reported to the court. However the number of human populations that could be considered is essentially unlimited and the number of contributors to a sample can be large, making it impractical to perform every possible WoE calculation, particularly for complex crime scene profiles. We propose instead the use of only the database that best matches the ancestry of the queried contributor, together with a substantial F_ST adjustment. To investigate the degree of conservativeness of this approach, we performed extensive simulations of one- and two-contributor crime scene profiles, in the latter case with, and without, the profile of the second contributor available for the analysis. The genotypes were simulated using five population databases, which were also available for the analysis, and evaluations of WoE using our heuristic rule were compared with several alternative calculations using different databases. Using F_ST = 0.03, we found that our heuristic gave WoE more favourable to the defence than alternative calculations in well over 99% of the comparisons we considered; on average the difference in WoE was just under 0.2 bans (orders of magnitude) per locus. The degree of conservativeness of the heuristic rule can be adjusted through the F_ST value. We propose the use of this heuristic for DNA profile WoE calculations, due to its ease of implementation, and efficient use of the evidence while allowing a flexible degree of conservativeness.     

Postmortem vitreous Beta-hydroxybutyrate: interpretation in a forensic setting*

Abstract: Vitreous beta‐hydroxybutyrate (BHB) was retrospectively analyzed in 1795 forensic cases using the Pointe Scientific method. Comparison of vitreous BHB with vitreous glucose in 1781 of the cases showed moderately good correlation r = 0.731. Comparison with blood alcohol levels in 1561 of the cases showed no correlation r = ?0.053. Vitreous BHB was a marker of diabetic ketoacidosis when above 6.0 mM with a vitreous glucose over 200 mg/dL. It was an indicator (>50%) for alcoholic ketoacidosis when above 6.0 mM with a vitreous glucose below 200 mg/dL. Recommendations for interpretation of vitreous BHB: <0.4 mM normal; 0.41–1.2 mM slightly elevated, rarely (<1%) of concern; 1.21–2.0 mM moderately elevated, less rarely (2.5%) of concern; 2.01–6.0 mM significantly elevated, frequently of concern (12–48%); >6.0 mM usually (100% in this study) indicated life‐threatening conditions. Vitreous BHB was helpful evaluating cases with ketogenic conditions, especially diabetes and alcoholism.     

Structural analysis of human rib fracture and implications for forensic interpretation

Patterns of rib fractures are of significant clinical and forensic interest. Linking patterns of rib fracture with specific physical events provides a foundation for understanding the nature of traumatic events that are associated with rib fracture in forensic contexts. In this study, isolated human ribs (n = 8) were end-loaded to failure to investigate: (i) local deformations (bone strain) prior to and during structural failure, (ii) location of ultimate failure, and (iii) fracture mode. Structural properties of ribs were used to calculate theoretical stresses to determine whether such calculations could be used to predict site of fracture. Ribs fractured on the sternal side of midshaft in all experiments, but mode of failure varied with transverse, buckle, spiral, and "butterfly" fractures observed. Comparison of calculated stress with observed strain values suggest that experimental, rather than theoretical, approaches will be most productive in furthering understanding rib fracture in forensic contexts.     

荧光STR直接复合扩增试剂缓冲体系的研制

目的研制适用于数据库样本荧光STR直接复合扩增体系。方法针对常规血卡、FTA和903血卡样本,配制扩增缓冲液基准母液,采用不同配方的扩增缓冲体系进行直接扩增及检测。考察不同种类增强剂、4种商业化DNA聚合酶、不同复性温度和终延伸时间对检材的检测效果,并验证优化体系的适应性。结果采用本文所建体系对各类血卡样本进行检验,均可获得样本清晰、完整的STR分型。体系选择BSA\Tween20\DMSO\甘油等增强剂组合、Typer热启动聚合酶1.5U/10μL、57～59℃复性温度、30～50min终延伸时间,采用10μL体系即可对直径1.2mm FTA卡血样进行有效分型。结论本文所研制的缓冲体系能够满足常规血卡、FTA和903血卡样本直接扩增检验的需要。     

Development of a searchable major and trace element database for use in forensic soil comparisons

Forensic soil comparisons are normally undertaken on the basis of several physical, chemical and biological properties, but in all cases the interpretation of results is dependent on the availability of relevant contextual information. This paper summarises the results of major and trace element analyses performed using inductively coupled plasma atomic emission spectrometry and inductively coupled plasma-mass spectrometry on the < 150 µm size fraction of 1896 soil samples collected in connection with forensic investigations in England and Wales between 1999 and 2007. A number of new methods are described which facilitate inter-sample comparison. Although the available data do not provide uniform geographical coverage they do provide useful information which can assist police search investigations and they provide valuable contextual information which aids the evidential assessment of soil evidence when used in court. There is considerable scope to improve the database by increasing the geographical coverage and increasing the number of soil attributes which are included.     

Olanzapine-induced hyperglycemic ketoacidosis and corresponding acetone concentrations post-mortem: a forensic interpretation

Olanzapine has been shown to cause or have a contributory role in the development of hyperglycemia and diabetes mellitus. Without careful monitoring for the development of these conditions and control of the resulting adverse effects, patients receiving olanzapine may be at risk of developing fatal ketoacidosis. A review of post-mortem toxicological reports has revealed an increase in the incidence of post-mortem findings of acetone in decedents who were taking olanzapine over the past decade. A review of the current literature and a comprehensive review of case histories and toxicological findings were conducted at the Centre of Forensic Sciences (Toronto, Ontario). Olanzapine concentrations ranging from <62.5 to 858 ng/mL and acetone concentrations as high as 95 mg/dL were detected concurrently. Due to the unstable nature of olanzapine, in several instances quantitation was not possible despite elevated responses during qualitative screening procedures. Five cases suggesting olanzapine-induced ketoacidosis were identified based on the case history and toxicological findings. These data have been compiled and examined with respect to acetone concentrations following olanzapine use and the forensic relevance of post-mortem olanzapine and acetone concentrations are discussed.     

利用腭皱特征进行同一认定的指标体系构建

目的根据腭皱的形态图特征,进行口腔腭皱在法医学同一认定的指标体系构建。方法收集100例成年人腭皱模型,依据腭皱的形状、数量、位置分布等特征对腭皱形态图进行全面系统的编码。编码顺序采用英文字母按照先右侧再左侧,先前部再后部的顺序编码,并且右、左侧编码以破折号连接。最后依据编码,统计分析腭皱形态分布特征。结果 100例腭皱形态图中,个体间未见完全一致者,每个个体不论男性与女性均表现有独特的腭皱形态图;且同一个体左右侧单条腭皱的形态及分布亦不同。波浪形腭皱所占比例最大（23.03%）,三分叉形出现比例最小（0.74%）,不同性别的波浪形及曲线形腭皱所占比例均较大,女性波浪形（22.7%）及曲线形（18.28%）;男性波浪形（24.11%）及曲线形（21.43%）。结论口腔腭皱法医学同一认定的指标体系构建,将为法医学的同一认定提供一种新的方法。     

Trends in forensic DNA database:transnational exchange of DNA data

The transnational exchange of forensic DNA data has become a modern trend in fighting cross-border crime,terrorism and illegal immigration.Forensic DNA data all...