Using the likelihood ratio in bloodstain pattern analysis

There is an apparent paradox that the likelihood ratio (LR) approach is an appropriate measure of the weight of evidence when forensic findings have to be evaluated in court, while it is typically not used by bloodstain pattern analysis (BPA) experts. This commentary evaluates how the scope and methods of BPA relate to several types of evaluative propositions and methods to which LRs are applicable. As a result of this evaluation, we show how specificities in scope (BPA being about activities rather than source identification), gaps in the underlying science base, and the reliance on a wide range of methods render the use of LRs in BPA more complex than in some other forensic disciplines. Three directions are identified for BPA research and training, which would facilitate and widen the use of LRs: research in the underlying physics; the development of a culture of data sharing; and the development of training material on the required statistical background. An example of how recent fluid dynamics research in BPA can lead to the use of LR is provided. We conclude that an LR framework is fully applicable to BPA, provided methodic efforts and significant developments occur along the three outlined directions.     

Minor or adult? Introducing decision analysis in forensic age estimation

Nowadays, forensic age estimation takes an important role in worldwide forensic and medico-legal institutes that are solicited by judicial or administrative authorities for providing an expert report on the age of individuals. The authorities’ ultimate issue of interest is often the probability that the person is younger or older than a given age threshold, which is usually the age of majority. Such information is fundamental for deciding whether a person being judged falls under the legal category of an adult. This is a decision that may have important consequences for the individual, depending on the legal framework in which the decision is made. The aim of this paper is to introduce a normative approach for assisting the authority in the decision-making process given knowledge from available findings reported by means of probabilities. The normative approach proposed here has been acknowledged in the forensic framework, and represents a promising structure for reasoning that can support the decision-making process in forensic age estimation. The paper introduces the fundamental elements of decision theory applied to the specific case of age estimation, and provides some examples to illustrate its practical application.     

迈向“过程导向信任”的刑事死因鉴定争议解决机制

中国当今刑事鉴定争议频发。其中当事人与办案机关鉴定冲突最剧烈、不满手段最多样,且其社会影响最大者,目前主要聚集在部分死因鉴定领域。该类鉴定争议既滋生过度重复鉴定,更促使部分当事人上访、闹事,一度还以此衍生出暴力性群体事件。死因鉴定争议的发生,主要源于影响鉴定意见可信性的一系列因素,而非仅因为、甚或主要基于鉴定意见的客观可靠性。因此,为重塑中国刑事死因鉴定的公信力,必须走向从实践出发的法律研究与制度建构立场,以回应办案部门创建、并亟须理论提炼与立法改良的“过程导向信任”的鉴定争议解决机制。其关键措施,是通过死因鉴定程序的开放性与当事人双方（包括其聘请的法医专家）的充分参与性,从而实现鉴定意见的可信性或当事人可接受性;并以此领域的鉴定争议解决为突破口,进行鉴定制度改革,以提升中国整个刑事司法鉴定的公信力与可信性。     

The Reliability of Pattern Classification in Bloodstain Pattern Analysis—PART 2: Bloodstain Patterns on Fabric Surfaces,

This study was designed to produce the first baseline measure of the reliability of bloodstain pattern classifications on fabric surfaces. Experienced bloodstain pattern analysts classified bloodstain patterns on pairs of trousers that represented three fabric substrates. Patterns also varied in type (impact, cast‐off, expiration, satellite stains from dripped blood, and transfer) and extent. In addition, case summaries that accompanied each pattern contained contextual cues that either supported the correct answer (i.e., positive bias), were misleading toward an incorrect answer (i.e., negative bias), or contained no directional information (i.e., neutral). Overall, 23% percent of the resulting classifications were erroneous. The majority (51%) of errors resulted from analysts misclassifying satellite stains from dripped blood. Relative to the neutral information, the positive‐bias information increased correct classifications and decreased erroneous classifications, and the negative‐bias information decreased correct classifications and increased erroneous classifications. The implications of these findings for BPA are discussed.     

Turf wars: authority and responsibility for the investigation of mass graves

Mass graves are complex products of large-scale crimes. Such scenes pose four conceptual challenges to investigators and forensic experts: the individual victim, the crime, the setting, and the statistical. Exhumation and post-mortem examination of mortal remains with associated personal and forensic evidence require integrated management of core forensic personnel including investigators, archaeologists, anthropologists, odontologists and pathologists, among whom there is overlapping expertise. The key to avoiding competition and ill-will among experts is to recognize that all such experts should be enabled to make known how their expertise matches with the temporal and spatial boundaries of victim, crime and setting. In turn, they should be apprised of where they fit into the overall judicial process and their limits within the investigation. Consequently, each expert requires access to the factual background of the case, to the site and its contents throughout the investigation. Each forensic team member has a responsibility to influence the investigation--throughout its course when possible--to make findings within their areas of expertise, and to make these available to the rest of the team so as to contribute most meaningfully to the aims of the investigation, both forensic and humanitarian. The on-site crime scene manager has an overarching role to enable integrated access to the complete scene and its contents by each forensic expert team member. In other words, the forensic scientist is given access and the ability to influence the investigation while control of evidence from the site as to identity and criminal activity are maintained by the crime scene manager. This contribution is directed at both the crime scene manager and each forensic expert; it describes the essential spatial and temporal parameters of an expert's opinion so as to encourage cooperation, and discourage conflict, within the forensic team.     

Blood-spatter patterns: hands hold clues for the forensic reconstruction of the sequence of events

Biologic and nonbiologic traces on the hands are of particular importance for the forensic reconstruction of shooting incidents; gunpowder residue analysis in particular helps determine whether the gunshot is close range or distant. In crime scene investigation, knowledge about the morphology of bloodstain patterns-including gunshot-related back spatter-has increased since various experimental examinations have been performed in the last years; nowadays, these traces are frequently used for forensic crime scene reconstruction. The goal of this study was to deduce the position and orientation of the hands, and therefore the firearm, according to the bloodstain patterns on the hands of the deceased. For this purpose blood-spatter stains on the hands were examined on site in 5 suicides caused by gunshot. In all cases, forensically relevant conclusions regarding forensic reconstruction were enabled through close examination of the spatter marks. Therefore, in shooting incidents, analysis and documentation of blood-spatter findings on the hands is recommended before hands are tested for gunpowder residue or wrapped for the transport of the body.     

Bloodstain pattern analysis--casework experience

The morphology of bloodstain distribution patterns at the crime scene carries vital information for a reconstruction of the events. Contrary to experimental work, case reports where the reconstruction has been verified have rarely been published. This is the reason why a series of four illustrative cases is presented where bloodstain pattern analysis at the crime scene made a reconstruction of the events possible and where this reconstruction was later verified by a confession of the offender. The cases include various types of bloodstains such as contact and smear stains, drop stains, arterial blood spatter and splash stains from both impact and cast-off pattern. Problems frequently encountered in practical casework are addressed, such as unfavourable environmental conditions or combinations of different bloodstain patterns. It is also demonstrated that the analysis of bloodstain morphology can support individualisation of stains by directing the selection of a limited number of stains from a complex pattern for DNA analysis. The complexity of real situations suggests a step-by-step approach starting with a comprehensive view of the overall picture. This is followed by a differentiation and analysis of single bloodstain patterns and a search for informative details. It is ideal when the expert inspecting the crime scene has also performed the autopsy, but he definitely must have detailed knowledge of the injuries of the deceased/injured and of the possible mechanisms of production.     

A new examination program for forensic assessment: performance of computers in medicine

Computerizing of medicine is expected to increase very rapidly in the next few years. This will bear new questions for forensic judgement. We report a case and our expert opinion concerning the use of a very simple computer program at a private hospital to obtain comments on laboratory findings. Furthermore we discuss questions we consider to be of importance for forensic judgement in this field.     

以审判为中心的庭审模式对法医出庭质证的挑战

以审判为中心的庭审模式是当今诉讼改革的主要方向,案件庭审实质化是诉讼改革的主要目标,在此背景下,法医鉴定人出庭质证将会实质化、常态化。为此,最高人民法院等部门出台了保障鉴定人出庭的相关规定、规则。法医鉴定意见质证实质化要求法医鉴定人在出庭时履行相关义务:尊重法庭、如实回答提问、释明鉴定意见。当前法医参加庭审质证中存在法医鉴定人出庭率低、鉴定意见的法律性质不明确、鉴定人出庭的具体要求不明确、与包括专家辅助人在内的其他专家证据形式的冲突等问题。为此,笔者向法医鉴定人提出三点建议:不断学习,提升专业技能;加强修炼,提高法律知识;注重实践,强化表达能力。     

开发高灵敏度血痕发光试剂用于法医现场检测

目的开发高灵敏度血痕发光试剂用于法医现场检测。方法本项目通过借鉴ECL发光的原理,通过化学电子链的乒乓共轭激活原理,使用均匀设计实验方法优化条件,合成多个新化合物,开发出新型高灵敏度血痕发光试剂。结果本项目开发的高灵敏度血痕发光试剂灵敏度高,发光时间长,在血液稀释1000倍的情况下,使用Chemi Scope3300化学发光成像系统读取荧光值,经过灰度转化最高值达到56,发光时间达到10分钟。结论本项目成功开发了高灵敏度血痕发光试剂,可以应用于法医现场检测。     

Quantitative Differentiation of Bloodstain Patterns Resulting from Gunshot and Blunt Force Impacts

Bloodstain pattern analysis (BPA) provides significant evidentiary value in crime scene interpretation and reconstruction. In this work, we develop a quantitative methodology using digital image analysis techniques to differentiate impact bloodstain patterns. The bloodstain patterns were digitally imaged and analyzed using image analysis algorithms. Our analysis of 72 unique bloodstain patterns, comprising more than 490,000 individual droplet stains, indicates that the mean drop size in a gunshot spatter pattern is at most 30% smaller than the mean drop stain size in blunt instrument patterns. In contrast, we demonstrate that the spatial distribution of the droplet stains—their density as a function of position in the pattern—significantly differs between gunshot and blunt instrument patterns, with densities as much as 400% larger for gunshot impacts. Thus, quantitative metrics involving the spatial distribution of droplet stains within a bloodstain pattern can be useful for objective differentiation between blunt instrument and gunshot bloodstain patterns.     

Whole bovine blood use in forensic research: Sample preparation and storage considerations

Mammalian whole blood sources are often used for forensic research and training when human samples cannot be sourced. While porcine, ovine and equine blood have been shown to be viable alternatives to whole human blood for forensic purposes, procurement can still pose a problem, especially for smaller and remote institutions. This work explores the use of whole bovine blood for basic bloodstain simulation. Sample preparation through the addition of ACD-A anticoagulant was optimized and storability was explored. Viscosity, surface tension, density, and packed cell volume, four fluid properties relevant to bloodstain pattern analysis, were monitored over four days and in two temperature conditions. Linear mixed models accounting for variation in the donor demonstrated that these fluid properties of the bovine blood changed predictably over time and with temperature. Whole bovine blood with 12.5% v/v ACD-A was found to be viable for use in basic bloodstain simulation at ambient and physiological temperature.     

论专家辅助人意见——以刑事辩护为视角的分析

我国2012年新《刑事诉讼法》首次设立专家辅助人制度，对鉴定意见的质证提供了技术上的支持，对于刑事辩护来说意义重大。从证据法的角度看来，专家辅助人意见具有言词证据、意见证据、弹劾证据的多重属性，因此意见的内容应围绕鉴定意见中的专门性问题，并结合《刑事诉讼法》及相关司法解释对鉴定意见的审查判断规则来提出；而法庭对于鉴定意见的审查也应从准入资格与可靠性两方面进行，以免专家辅助人意见替代鉴定意见来主导审判。     

Expert Testimony Regarding Child Witnesses: Does It Sensitize Jurors to Forensic Interview Quality?

Does expert testimony on forensic interviews with children help adults distinguish between poorly conducted and well-conducted interviews? This study evaluates the effects of social framework expert testimony regarding child witnesses in a case involving allegations of child sexual abuse. A 2 (Expert Testimony: present or absent) × 3 (Child Forensic Interview Quality: poor, typical, or good) × 2 (Child’s Age: 4- or 10-year-old) factorial design was used to examine whether expert testimony is prejudicial or beneficial to jurors (N = 463). The results revealed that, without expert testimony, mock jurors did not consider the forensic interview quality when reaching a verdict. However, with expert testimony, mock jurors were more likely to render guilty verdicts if the interview quality was good versus poor. Further expert testimony increased mock jurors’ knowledge about child witnesses. These findings suggest that expert testimony related to the impact of interview techniques on the reliability of children’s reports may assist fact-finders in evaluating child abuse cases.     

Bloodstain pattern analysis in a case of fatal varicose vein rupture

Rupture of a varicose vein is a rare cause of sudden death. It occurs when the failure of venous valves causes an increase in venous pressure great enough to provoke rupture of the blood vessel. When it does happen, the victim is often found surrounded by a pool of blood, and the examination of the scene can mislead the forensic team to think of violent death. Until now, the bloodstain patterns in these fatal cases have not been described. An examination of the bloodstain pattern in a case of fatal varicose vein rupture in an 84-year-old man is here reported.     

Presentation of a three-banded allele pattern--analysis and interpretation

The Israel police forensic biology laboratory received as an item of evidence in an attempted murder case, a pair of trousers belonging to a suspect. A bloodstain was observed on the trousers and analyzed by STR typing for nine loci using the Promega GenePrint STR silver stain detection kits. The genetic profile defined was found to be identical to that of the victim's at all nine loci. Within this profile a three-banded allele pattern was observed at the D16S539 locus, both in the bloodstain and in the victim's reference blood sample. Confirmation of this phenomenon was accomplished by amplifying the extracted DNA from both the trousers and the victim's blood sample using the PowerPlex 16 kit by Promega and the AmpFlSTR SGM Plus kit by Perkin Elmer, followed by analysis of the amplification products by capillary electrophoresis on the ABI prism 310 genetic analyzer. The same three-banded allele pattern was observed at the D16S539 locus in both specimen and reference DNA, using each of the three kits. Three additional loci located on chromosome 16 (D16S3407, D16S2617 and D16S3082), not employed for forensic identification, were also analyzed and did not show three-banded allele pattern.     

A collaborative approach for incorporating forensic case data into crime investigation using criminal intelligence analysis and visualisation

There is an increasing awareness that the articulation of forensic science and criminal investigation is critical to the resolution of crimes. However, models and methods to support an effective collaboration between the partners are still poorly expressed or even lacking.Three propositions are borrowed from crime intelligence methods in order to bridge this gap: (a) the general intelligence process, (b) the analyses of investigative problems along principal perspectives: entities and their relationships, time and space, quantitative aspects and (c) visualisation methods as a mode of expression of a problem in these dimensions.Indeed, in a collaborative framework, different kinds of visualisations integrating forensic case data can play a central role for supporting decisions. Among them, link-charts are scrutinised for their abilities to structure and ease the analysis of a case by describing how relevant entities are connected. However, designing an informative chart that does not bias the reasoning process is not straightforward. Using visualisation as a catalyser for a collaborative approach integrating forensic data thus calls for better specifications.     

Morphologic studies in criminal justice--requirements and reality

A critical analysis is given of the investigation and examination of fatalities for the public prosecution office and for the courts. Rationalistic simplifications in legal quarters, changes in legal procedures and bureaucracy have had negative effects on the field of forensic medicine. It is questionable whether forensic science today can fulfil the scientific demands with regard to a complete and thorough explanation of the cause of death. The reduced interest in expert opinions concerning the pattern of injuries that can help in the reconstruction of the act or in judging the intention and guilt of the perpetrator is a striking and alarming development in criminal justice. Medical examinations in the somatic field are no longer used enough in forensic cases; with regard to the administration of justice, the role of the forensic expert is limited to the postmortem findings and the cause of death. On the other hand, there is increased interest in the expert opinion of psychologists, psychiatrists and specialists in the field of drugs and alcohol. The fact that the number of autopsies and histological as well as toxicological examinations ordered by the public prosecutor is rather small has serious and negative implications for establishing the truth. Such orders are merely dependent on the circumstance of death and the situation in which the body was found. However, the external circumstances can be misleading or they can be manipulated. That is why some crimes are not revealed. In the Federal Republic of Germany, if there is no suspicion of external violence permission is granted for corpses to be buried without the cause of death being clarified by autopsy. However, the fact that the opinions of forensic specialists differ regarding this development in the administration of justice must also be criticized. There is an increasing tendency for investigations to be carried out only if they are ordered by the prosecutor and for questions to be answered only if they are asked officially. Even our colleagues are influenced too much by external circumstances and consider an autopsy unnecessary if the cause of death seems to be clear (for instance in cases of hanging, drowning or bleeding to death). Second autopsies have shown that the thoroughness and the quality of the first autopsy often leave much to be desired. It is, for instance, unforgivable if organs are described without being examined. Special interest is afforded to the necessity for the significance of histological examinations.(ABSTRACT TRUNCATED AT 400 WORDS)     

Improved Area of Origin Estimation for Bloodstain Pattern Analysis Using 3D Scanning

An important component of crime scene reconstruction is bloodstain pattern analysis (BPA). Where BPA concerns impact patterns, estimating the area of origin is critical information for scene reconstruction. Traditionally, this is achieved by measuring individual bloodstains and performing trigonometric calculations; however, 3D scanning has been proposed as a viable alternative for overcoming logistical and practical concerns with the manual method. Therefore, this project aimed to establish whether the FARO Focus 3D scanner and FARO Zone 3D software can improve the accuracy of area of origin estimates relative to the manual method. We created a series of eight bloodstain impact patterns and performed paired analysis using the two methods to estimate areas of origin for each pattern. Our data suggested that FARO-derived estimates were generally more accurate than using the manual method. FARO-estimated heights of origin areas were generally closer to the true distance. Both methods underestimated the distance from the wall for most patterns originating 150mm or greater from the wall, but overestimated distances for patterns originating closer to the wall. The degree to which distances were underestimated increased significantly the further the blood source was from the wall and was greater for FARO-derived estimates. The results of this research contribute to the validation of these instruments for operational implementation for BPA and should be considered alongside the practical benefits of 3D scanning relative to manual methods. Further, 3D scanning can provide reliable BPA reconstruction documentation for technical review and court presentation.     

The Reliability of Pattern Classification in Bloodstain Pattern Analysis,Part 1: Bloodstain Patterns on Rigid Non‐absorbent Surfaces

This study was designed to produce the first baseline measure of reliability in bloodstain pattern classification. A panel of experienced bloodstain pattern analysts examined over 400 spatter patterns on three rigid non‐absorbent surfaces. The patterns varied in spatter type and extent. A case summary accompanied each pattern that either contained neutral information, information to suggest the correct pattern (i.e., was positively biasing), or information to suggest an incorrect pattern (i.e., was negatively biasing). Across the variables under examination, 13% of classifications were erroneous. Generally speaking, where the pattern was more difficult to recognize (e.g., limited staining extent or a patterned substrate), analysts became more conservative in their judgment, opting to be inconclusive. Incorrect classifications increased as a function of the negatively biasing contextual information. The implications of the findings for practice are discussed.