中国法医学会物证专业委员会法医DNA分析的若干建议

中国法医学会法医物证学专业委员会与国际法医遗传学会中文专委会于2006年10月在成都召开学术会议。我们的讨论强调有必要将国际法医遗传学会的信息及时传递到中国。因此,按照国际法医遗传学会的指南,我们推荐混合斑分析,法医DNA数据库及新遗传标记选择标准供同行参考。     

Gait analysis in forensic medicine*

Recordings from video surveillance systems are used as evidence from crime scenes. It would be useful to perform comparisons between disguised perpetrators and suspects based on their gait. We applied functional anatomical and biomechanical knowledge to analyze the gait of perpetrators, as recorded on surveillance video. Using a structured checklist, which addresses the single body segments during gait, we were able to give a statement concerning the gait patterns. Characteristic parameters were, e.g., varus instability in the knee at heel strike, and larger lateral flexion of the spinal column to one side than the other. Based on these characteristic features, we are able to state with reasonable certainty whether the suspect could be the perpetrator, but it is not possible to identify the perpetrator positively. Nevertheless, we have been involved in several cases where the court has found that this type of gait analysis was a valuable tool.     

Investigating demodex in forensic autopsy cases

Demodex is an ectoparasite living in the skin as a nonpathogen or a pathogen. It is also known that demodex acts as a vector of pathogenic microorganisms. In this study, we have investigated the rate of occurrence and vitality of demodex in forensic autopsies that have a high risk of contamination by infected organisms. The study, which was cross-sectional, conducted on 100 autopsy cases: 77 of the bodies were male and 23 female. The average age was 41. The samples were taken from the forehead, nose, cheeks, eyelashes and the temporal areas using the standardized skin surface biopsy and hair epilation techniques that were modified for this study. The data obtained were assessed statistically. Demodex was determined in 10% of all the cases. The cases revealed that demodex increased in old age and was more frequently seen in people with fair complexion. It was most frequently found in the forehead and the cheek. The longest postmortem interval in the positive cases was 55 h. The relationship between the postmortem interval and the presence of demodex was not statistically significant. Considering the fact that demodex, which is transmitted from human to human through skin contact, acts as a vector of pathogenic organisms and can stay alive in dead bodies for a long time, we think that the personnel performing autopsies without taking the necessary precautions are under risk.     

Deterring gun crime materially using forensic coatings

Surface coatings that can help deter and solve gun crime are described. These nanoengineered coatings have been applied and evaluated on brass cartridge cases, where they increase associative forensic evidence through nanotag donation to the handler and the retention of handler's DNA. In future we expect this approach to be used for other surfaces and conditions.     

Characterising stutter in forensic STR multiplexes

Stutter is an artefact seen when amplifying short tandem repeats and typically occurs at one repeat unit shorter in length than the parent allele. In forensic analysis, stutter complicates the analysis of DNA profiles from multiple contributors, known as mixed profiles, a common profile type. Consequently it is important to both understand and predict stutter behaviour in order to improve our understanding of the resolution and interpretation of these profiles. Whilst stutter is well recognised and documented, little information is available that identifies and quantifies what influences the formation of stutter. In this work we use a novel approach to examine this. We have used synthetic oligonucleotides comprising multiple repeat units to test; the influence of repeat number, the influence of repeat sequence and the impact of interruptions to the repeat sequence length. Using multiple replicates allows detailed statistical analysis. We have confirmed a linear relationship between stutter ratio and repeat number. We have shown that increased A-T content increases stutter ratio and that interruptions in repeating sequences decreased stutter ratios to levels similar to the longest uninterrupted repeat stretch. We also found that there was no relationship between stutter ratio and repeat number for a repeat unit with an A-T content of 1/4 and that half of the interrupted repeat sequences stuttered significantly less than their longest uninterrupted repeat stretches. We have applied the knowledge gained to examine specific features of the loci present in the AmpFlSTR^® SGM Plus^® multiplex kit used in our laboratory.     

Consensus on validation of forensic voice comparison

Since the 1960s, there have been calls for forensic voice comparison to be empirically validated under casework conditions. Since around 2000, there have been an increasing number of researchers and practitioners who conduct forensic-voice-comparison research and casework within the likelihood-ratio framework. In recent years, this community of researchers and practitioners has made substantial progress toward validation under casework conditions becoming a standard part of practice: Procedures for conducting validation have been developed, along with graphics and metrics for representing the results, and an increasing number of papers are being published that include empirical validation of forensic-voice-comparison systems under conditions reflecting casework conditions. An outstanding question, however, is: In the context of a case, given the results of an empirical validation of a forensic-voice-comparison system, how can one decide whether the system is good enough for its output to be used in court? This paper provides a statement of consensus developed in response to this question. Contributors included individuals who had knowledge and experience of validating forensic-voice-comparison systems in research and/or casework contexts, and individuals who had actually presented validation results to courts. They also included individuals who could bring a legal perspective on these matters, and individuals with knowledge and experience of validation in forensic science more broadly. We provide recommendations on what practitioners should do when conducting evaluations and validations, and what they should present to the court. Although our focus is explicitly on forensic voice comparison, we hope that this contribution will be of interest to an audience concerned with validation in forensic science more broadly. Although not written specifically for a legal audience, we hope that this contribution will still be of interest to lawyers.     

Information assurance in a distributed forensic cluster

When digital forensics started in the mid-1980s most of the software used for analysis came from writing and debugging software. Amongst these tools was the UNIX utility ‘dd’ which was used to create an image of an entire storage device. In the next decade the practice of creating and using ‘an image’ became established as a fundamental base of what we call ‘sound forensic practice’. By virtue of its structure, every file within the media was an integrated part of the image and so we were assured that it was wholesome representation of the digital crime scene. In an age of terabyte media ‘the image’ is becoming increasingly cumbersome to process, simply because of its size. One solution to this lies in the use of distributed systems. However, the data assurance inherent in a single media image file is lost when data is stored in separate files distributed across a system. In this paper we assess current assurance practices and provide some solutions to the need to have assurance within a distributed system.     

论声纹鉴定意见的表述形式

本文针对目前国内外讨论比较热烈的声纹鉴定意见表述问题进行了评述.首先介绍了实践中正在使用的听觉分析法、声谱比对分析法、声学分析法、听觉-声学分析法和说话人自动识别五种鉴定方法,指出了各种方法的优缺点;然后对现存的二元判决、可能性等级、似然比和英国立场声明四种鉴定意见表述形式进行了介绍和评析,通过分析发现,上述四种意见表述形式都存在一定的问题,实践中选择何种形式表述鉴定意见要综合考虑其科学性、逻辑性、现实性和可行性等多种价值选项;最后认为解决该问题的根本方法是各相关领域的专家应加强在鉴定方法上的合作性的基础研究.     

Clinical forensic medicine

This article discusses the merits of participation by medical examiners in the area of clinical forensic medicine. The present connotation that we deal after the fact should be abandoned with enhanced involvement in assisting the living. The paper focuses on a broad range of categories where forensic scientists by virtue of their training and experience could be most helpful in the application of medical knowledge to the solution of questions of law.     

The distinction between discriminability and reliability in forensic science

Forensic science plays an increasingly important role in the criminal justice system; yet, many forensic procedures have not been subject to the empirical scrutiny that is expected in other scientific disciplines. Over the past two decades, the scientific community has done well to bridge the gap, but have likely only scratched the tip of the iceberg. We offer the discriminability-reliability distinction as a critical framework to guide future research on diagnostic-testing procedures in the forensic science domain. We argue that the primary concern of the scientist ought to be maximizing discriminability and that the primary concern of the criminal justice system ought to be assessing the reliability of evidence. We argue that Receiver Operating Characteristic (ROC) analysis is uniquely equipped for determining which of two procedures or conditions has better discriminability and we also demonstrate how estimates of reliability can be extracted from this Signal Detection framework.     

The concept of free will and forensic psychiatry

This text examines how conceptions of free will impact on legal systems and forensic psychiatry: free will is generally regarded as a prerequisite for responsibility, criminal responsibility included, while forensic psychiatry to a large extent deals with the limits imposed on responsibility by mental disorder. First we discuss the question of whether there is and has been such an impact. The answer is yes: different conceptions of free will have inspired different systems of law and forensic psychiatry, as becomes clear when looking at the accountability doctrine as compared to the unique Swedish system rejecting this doctrine. However, there is no necessary connection between doctrines of responsibility and conceptions of free will, since the former primarily says something about when someone should be held responsible and the latter says something about when someone really is free in a sense relevant to responsibility. This leads to the second question: should conceptions of free will have an impact on law and forensic psychiatry? We argue: that they should not, given the implausibility the normative theory retributivism, which posits a direct connection between free will and punishment. More importantly, questions of free will are complicated and unresolved philosophical issues that are better left out of the everyday decision-making incumbent on the legal and psychiatric systems. Instead, we recommend using an empirically useful and gradual conception of autonomy to facilitate the determination of legal responsibility. This autonomy conception, being neutral on the question of free will, eliminates the need to take a stand on it.     

Computer forensic timeline visualization tool

Computer Forensics is mainly about investigating crime where computers have been involved. There are many tools available to aid the investigator with this task. We have created a prototype of a new type of tool called CyberForensic TimeLab where all evidence is indexed by their time variables and plotted on a timeline. We believed that this way of visualizing the evidence allows the investigators to find coherent evidence faster and more intuitively. We have performed a user test where a group of people has evaluated our prototype tool against a modern commercial computer forensic tool and the results of this preliminary test are very promising. The results show that users completed the task in shorter time, with greater accuracy and with less errors using CyberForensic TimeLab. The subjects also experienced that the prototype were more intuitive to use and that it allowed them to easier locate evidence that was coherent in time.     

Recovery of DNA for forensic analysis from lip cosmetics.

To obtain a reference DNA profile from a missing person, we analyzed a variety of personal effects, including two lip cosmetics, both of which gave full DNA profiles. Further investigations were undertaken to explore this previously unreported source of DNA. We have tested a range of brands and types of lip cosmetics. Our studies have revealed that lip cosmetics are an excellent source of DNA, with almost 80% of samples giving a result. However, artifacts are frequently observed in the DNA profiles when Chelex is used for the DNA extraction and additional DNA purification procedures are required to ensure that an accurate DNA profile is obtained.     

Topographies of forensic practice in Imperial Germany

This article examines the topography and “cultural machinery” of forensic jurisdictions in Imperial Germany. It locates the sites at which boundary disputes between psychiatric and legal professionals arose and explores the strategies and practices that governed the division of expert labor between them. It argues that the over-determined paradigms of ‘medicalization’ and ‘biologization’ have lost much of their explanatory force and that historians need to refocus their attention on the institutional and administrative configuration of forensic practices in Germany. After first sketching the statutory context of those practices, the article explores how contentious jurisdictional negotiations pitted various administrative, financial, public security, and scientific interests against one another. The article also assesses the contested status of psychiatric expertise in the courtroom, as well as post-graduate forensic psychiatric training courses and joint professional organizations, which drew the two professional communities closer together and mediated their jurisdictional disputes.     

The routine use of C-reactive protein in forensic investigations

In clinical medicine, C-reactive protein (CRP) is extensively used as a general marker for immune system activation, and post-mortem applicability has been established [M.Q. Fujita, B.L. Zhu, K. Ishida, L. Quan, S. Oritani, H. Maeda, Serum C-reactive protein levels in postmortem blood-an analysis with special reference to the cause of death and survival time, Forensic Sci. Int. 130 (2002) 160-166; L. Uhlin-Hansen, C-reactive protein (CRP), a comparison of pre- and post-mortem blood levels, Forensic Sci. Int. 124 (2001) 32-35]. We have analysed the routine use of CRP in non-selected cases. Scarcity of blood available for analysis is a common problem in forensic investigation, and in response to this we have developed a method using liver as a source. In 50 consecutive autopsy cases, we have evaluated method, validated results and discussed their interpretation. In three cases the analysis was not possible. For each of the remaining cases (n=47) we have analysed whole blood, serum and/or liver samples. 57% (n=25) had serum CRP > 10 mg/L. Serum levels were higher than in whole blood or liver. CRP levels in serum and whole blood samples were stable in more than one month after death, making storage for later analysis possible. Liver levels peaked at one week, but after one month putrefaction was obvious. CRP levels were independent of the post-mortem interval. The use of liver as a source has not yet been described in literature. Our results in liver samples correlate well with plasma results, and liver is a good post-mortem alternative when blood is not available. We conclude that CRP measurements are easy, viable and inexpensive in a forensic setting, and that the number of cases with CRP elevation is high in a non-selected forensic material. In cases of doubt, marked elevation of CRP is an indicator of natural mode of death, and in cases of trauma, it indicates vital reaction. It can be used as a pre-autopsy screening, leading to a more extensive search for diseases not easily diagnosed, such as sepsis or ketoacidosis.     

天津市法医DNA数据库的应用与发展

建立的天津市法医DNA数据库系统 ,将DNA分析技术的高效性与计算机系统的储存、高效检索的功能有机结合 ,实现了从受案到结案及建库的全程标准化、规范化、网络化管理。该系统启用一年多以来 ,为本地区侦查机关提供了百余起案件的破案线索 ,在多起重特大刑事案件的串并侦破中发挥了关键作用 ,技术破案率明显提高     

物证鉴定实验室的组织和服务体系

世界各国物证鉴定实验室组织结构有多种形式。本文综述了物证鉴定实验室的内部组织、上级组织和服务体系模式 ,分析讨论各种模式的特性和优缺点。物证鉴定实验室组织形式由多种因素决定 ,没有最佳模式     

法证披露模型:应当向法证专家披露什么和法证专家应当披露什么?

法律上的披露问题主要集中在检控方向辩护方提供或者隐瞒了哪些证据。在本文中,我们将披露的概念扩展到更广泛的情境下,在这种情境下,披露失误可能导致误判。我们引入了一个概念模型,即“法证信息披露”,它涉及哪些信息应该披露给法证检验人员,以及法证检验人员应当披露哪些信息。本文全面概述了四类利益相关者的动态交互:法证服务、调查、法律和外部利益相关者。我们通过五个问题讨论了法证信息披露模式的有效实施,即如果要向法证检验人员或者由法证检验人员提供最好的信息,以提高法证决策质素,并尽量减少偏差,则什么时候进行披露?披露什么?如何披露?向谁披露?为什么披露?     

Non-traumatic forensic neuropathology

The practicing Forensic Pathologist is likely to encounter case material in which either the cause of death or a major contribution to the cause of death is underlying damage to or disease of the central nervous system. While it is good practice in many instances to have a working relationship with a Department of Neuropathology, from which advice and practical help can be sought, there may be instances when the Forensic Pathologist needs to proceed on a basis of a working knowledge of Forensic Neuropathology up to and including how to examine the specimen and take tissue blocks for processing and subsequent histological examination. Some of the more common conditions of the central nervous system such as damage consequent to hypoxia-ischaemia, hypoglycemia and epilepsy, the encephalopathies associated with altered sodium concentration, deficiency due to Vitamin B(1) and various neurodegenerative diseases that manifest as dementia and include Alzheimer's disease, cortical Lewy body disease and the prion disorders, are outlined in this article.     

Evaluating expertise in forensic anthropology

The medicolegal system relies on the ability of experts and non-experts alike to make judgments about expertise and use those judgments to reach consequential decisions. Given the lack of standard criteria, mandatory certification, or licensure for establishing expertise required to practice forensic anthropology and testify as an expert witness, we sought to understand how individuals assess and identify expertise in forensic anthropology by using a social science tool called the Imitation Game. This tool assesses immersion in a specific area of study via discourse, with the premise that some individuals lacking expertise themselves imitate or attempt to pass as experts. For this project we recruited volunteers with varying expertise in forensic anthropology to participate in interviews which asked questions about the practice and structure of the discipline. Those interviews were transcribed, anonymized, and evaluated by other recruited individuals with varying expertise in forensic anthropology. Results found that judges who were experts in forensic anthropology performed better than non-expert judges in determining who was not an expert in forensic anthropology based on their anonymized responses; however, nearly half of the non-experts were still able to pass as experts in forensic anthropology. The difficulties in assessing expertise based on discourse interactions demonstrates the value and need for well-defined credentials and mandatory certification to practice forensic anthropology. This study demonstrates that accurately identifying expertise in forensic anthropology may be challenging for both experts and non-experts, especially when relying solely on interactional expertise rather than formal assessments of competency which directly elucidate contributory expertise.