ISFG: Recommendations on biostatistics in paternity testing

The Paternity Testing Commission (PTC) of the International Society for Forensic Genetics has taken up the task of establishing the biostatistical recommendations in accordance with the ISO 17025 standards and a previous set of ISFG recommendations specific to the genetic investigations in paternity cases. In the initial set, the PTC recommended that biostatistical evaluations of paternity are based on a likelihood ratio principle – yielding the paternity index, PI. Here, we have made five supplementary biostatistical recommendations. The first recommendation clarifies and defines basic concepts of genetic hypotheses and calculation concerns needed to produce valid PIs. The second and third recommendations address issues associated with population genetics (allele probabilities, Y-chromosome markers, mtDNA, and population substructuring) and special circumstances (deficiency/reconstruction and immigration cases), respectively. The fourth recommendation considers strategies regarding genetic evidence against paternity. The fifth recommendation covers necessary documentation, reporting details and assumptions underlying calculations. The PTC strongly suggests that these recommendations should be adopted by all laboratories involved in paternity testing as the basis for their biostatistical analysis.     

Sampling and statistical considerations for the Suchey–Brooks method for pubic bone age estimation: Implications for regional comparisons

Although the Suchey–Brooks (SB) system is currently the most widely used method for age-at-death estimation from the pubic bone, the system continues to evolve through stepwise improvements. Since the system was developed from a pubic bone sample derived mainly from North Americans, it is unclear how well it performs on populations from other continents. During the last decade, studies of the SB system on pubic bone samples from local populations in Europe and Asia have indicated regional differences in the relationship between age and pubic bone development. However, these studies have for the most part followed different research protocols, which make comparisons between their results less meaningful. It would be most useful if future regional analysis of the SB system were done in a rigorous and uniform fashion, following standard procedures. In this paper, sampling and statistical considerations are outlined that hopefully will help to standardize research on the SB system.     

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.     

双亲皆疑亲子鉴定STR分型亲权指数计算方法探讨

计算标准三联体亲子鉴定的PI值及探讨双亲皆疑亲子鉴定PI值计算的可靠方法 ,对常规STR分型鉴定结果 ,根据Eseen M ller计算理论 ,总结出标准三联体亲子鉴定计算PI值的 4个公式 :1/ p ,1/ ( 2 p) ,1/ (p +q) ,1/ ( 2p +2 q)。提出适用于双亲皆疑亲子鉴定的一种新的PI值计算方法 ,并与其他方法进行比较。认为该方法取值Y时 ,既考虑随机男女生孩子的可能性 ,也考虑假设父 (或假设母 )与随机个体生孩子的可能性 ,更符合随机原则。     

陈旧性骨骼DNA提取技术的研究

对陈旧性骨骼建立一个高回收率并能除去 PCR 反应抑制物的提取 DNA 的方法。采用 CTAB 法提取 DNA。结果显示,该方法不但能有效去除 PCR 抑制物,而且对水泡、火烧、土埋以及10年左右的骨骼所提取的 DNA 均能成功地进行荧光标记 STR 多基因座扩增检验。实验表明,该方法稳定,重复性好,适合陈旧骨骼标本的 DNA 提取。     

A method for calculating the strength of evidence associated with an earwitness's claimed recognition of a familiar speaker

The present paper proposes and demonstrates a method for assessing strength of evidence when an earwitness claims to recognize the voice of a speaker who is familiar to them. The method calculates a Bayes factor that answers the question: What is the probability that the earwitness would claim to recognize the offender as the suspect if the offender was the suspect versus what is the probability that the earwitness would claim to recognize the offender as the suspect if the offender was not the suspect but some other speaker from the relevant population? By “claim” we mean a claim made by a cooperative earwitness not a claim made by an earwitness who is intentionally deceptive. Relevant data are derived from naïve listeners' responses to recordings of familiar speakers presented in a speaker lineup. The method is demonstrated under recording conditions that broadly reflect those of a real case.     

Prediction of eye color from genetic data using Bayesian approach

Prediction of visible traits from genetic data in certain forensic cases may provide important information that can speed up the process of investigation. Research that has been conducted on the genetics of pigmentation has revealed polymorphisms that explain a significant proportion of the variation observed in human iris color. Here, on the basis of genetic data for the six most relevant eye color predictors, two alternative Bayesian network model variants were developed and evaluated for their accuracy in prediction of eye color. The first model assumed eye color to be categorized into blue, brown, green, and hazel, while the second variant assumed a simplified classification with two states: light and dark. It was found that particularly high accuracy was obtained for the second model, and this proved that reliable differentiation between light and dark irises is possible based on analysis of six single nucleotide polymorphisms and a Bayesian procedure of evidence interpretation.     

Measuring the validity and reliability of forensic likelihood-ratio systems

There has been a great deal of concern recently about validity and reliability in forensic science. This paper reviews for a broad target audience metrics of validity and reliability (accuracy and precision) which have been applied in forensic voice comparison and which are potentially applicable in other branches of forensic science. The metric of validity is the log likelihood-ratio cost (C_llr), and the metric of reliability is an empirical estimate of credible intervals. A revised procedure for the calculation of credible intervals is introduced.     

New perspectives in the use of ink evidence in forensic science: Part III: Operational applications and evaluation

The research reported in this series of article aimed at (1) automating the search of questioned ink specimens in ink reference collections and (2) at evaluating the strength of ink evidence in a transparent and balanced manner. These aims require that ink samples are analysed in an accurate and reproducible way and that they are compared in an objective and automated way. This latter requirement is due to the large number of comparisons that are necessary in both scenarios. A research programme was designed to (a) develop a standard methodology for analysing ink samples in a reproducible way, (b) comparing automatically and objectively ink samples and (c) evaluate the proposed methodology in forensic contexts.This report focuses on the last of the three stages of the research programme. The calibration and acquisition process and the mathematical comparison algorithms were described in previous papers [C. Neumann, P. Margot, New perspectives in the use of ink evidence in forensic science—Part I: Development of a quality assurance process for forensic ink analysis by HPTLC, Forensic Sci. Int. 185 (2009) 29–37; C. Neumann, P. Margot, New perspectives in the use of ink evidence in forensic science—Part II: Development and testing of mathematical algorithms for the automatic comparison of ink samples analysed by HPTLC, Forensic Sci. Int. 185 (2009) 38–50].In this paper, the benefits and challenges of the proposed concepts are tested in two forensic contexts: (1) ink identification and (2) ink evidential value assessment. The results show that different algorithms are better suited for different tasks. This research shows that it is possible to build digital ink libraries using the most commonly used ink analytical technique, i.e. high-performance thin layer chromatography, despite its reputation of lacking reproducibility. More importantly, it is possible to assign evidential value to ink evidence in a transparent way using a probabilistic model. It is therefore possible to move away from the traditional subjective approach, which is entirely based on experts’ opinion, and which is usually not very informative.While there is room for the improvement, this report demonstrates the significant gains obtained over the traditional subjective approach for the search of ink specimens in ink databases, and the interpretation of their evidential value.     

A simple method for calculating the probability of excluding paternity with any number of codominant alleles

A simple formula for calculating the probability of excluding paternity with a system determined by any number of codominant alleles was devised. Two computer programs are also described, which can be used when the genetic system is much more complicated.     

A cautionary note on the evaluation of genetic evidence from uniparentally transmitted markers

The combination of the information obtained from lineage genetic markers, such as mitochondrial DNA (mtDNA) and the non-homologous region of Y-chromosome, with data resulting from meiotically recombining loci (diploid/autosomal or haplodiploid/X chromosome) into a single likelihood ratio has been recently proposed. In this work we challenge this proposal and demonstrate that while the genetic evidence obtained from loci which reshuffle at meiosis is appropriate for individual probability calculations, mtDNA and Y-chromosome data are not and, consequently, that joining the evidential value of the two types of markers is generally inconsistent and should be avoided. The assumption of non-involvement of relatives must be clearly and explicitly stated and its acceptance must be left to the court decision.     

二元制抑或一元制：医疗纠纷鉴定模式的选择

医疗（事故）纠纷因专门性问题源于医疗事故技术鉴定和司法鉴定的＂二元制＂鉴定模式,致使纠纷解决的法律在选择适用上出现不同的结果,并造成了同一事实的处理结果尤其是赔偿的数额差异甚巨。《侵权责任法》的实施能否终结＂二元制＂鉴定模式,使冲突的相关规定、解释、解答等相关文本在法律适用上归于统一再次成为颇具争论的问题。基于医疗事故技术鉴定与司法鉴定结果在证据性质上的同一,有必要将医疗事故技术＂鉴定＂仅作为行政程序的内容,并进一步建立解决医疗纠纷的鉴定机制,体现鉴定作为证据的＂认定＂功能,以便实现医疗行为共担风险以及利益平衡的基本目标。     

广东广西地区5个群体9个STR基因座的频率调查

目的 调查广东汉族、广西汉族、广西侗族、广西壮族、广西苗族5个群体9个STR基因座多态性,探讨其在法医学检验中的应用价值。方法 应用AmpFISTR Profiler PlusTM荧光标记复合扩增系统,对广东广西5个群体4个民族的1191个无关个体的血样DNA进行9个STR基因座的复合扩增;用ABI 3100遗传分析仪对扩增产物进行分型,统计9个STR基因座的群体遗传学参数。结果 9个STR基因座在广东广西地区5个群体中的累积偶合率为1.51×10-11～8.08×10-11,累积非父排除率为0.99981—0.99990。,结论 该9个STR基因座可满足汉族、壮族、侗族、苗族群体法医学的个体识别及亲权鉴定的需要。     

中国“罪犯DNA数据库”STR基因座研究

选择合适的 STR基因座 ,建立中国“罪犯 DNA数据库”模式库。以 2 2 11名汉族、15 0名维吾尔族、10 4名回族群体为分析对象 ,提取罪犯血样 DNA,用复合 PCR和四色荧光技术检测了 D3S135 8、v WA、FGA、D8S1179、D2 1S11、D18S5 1、D5 S818、D13S317、D16 S5 39、TH0 1、TPOX、CSF1PO、D7S82 0等 13个 STR基因座及性别 Amelogenin基因座。在 13个 STR基因座中 ,除 TH0 1、TPOX基因座外 ,其余各基因座的个体鉴别能力 (DP)值均接近 0 .9,杂合度(H)均大于 0 .7,排除概率 (PE)大都在 0 .5以上 ,其中 FGA、D8S1179、D2 1S11和 D18S5 1基因座 DP≥ 0 .95 ,H≥ 0 .85 ,PE≥ 0 .6 5 ,表明它们在法医学上极有应用价值。TH0 1和 TPOX在多态性方面较差 (H分别为 0 .6 430和 0 .6 2 96 ,PE分别为0 .40 46和 0 .370 1) ,但也符合应用于法医学的要求。13个基因座的平均偶合率为 5× 10 - 1 5 ～ 1.2× l0 - 1 4 ,适合作为中国人群的遗传学标志 ,用于建立中国“罪犯 DNA数据库”     

A quantitative differentiation method for plastic bags by wide angle X-ray diffraction for tracing the source of illegal drugs

Thirty-three shopping bags, commonly encountered in the packaging of drug doses, were characterized by wide angle X-ray diffraction (WAXD). Using this single technique, without sample preparation, nearly all the considered samples could be differentiated, achieving a discriminating power of 0.992. The rather large degree of variability existing in grocery bags, even though they are mass produced, was shown, confirming that these items can be useful in tracing the source of illicit drug doses.     

11个Y—STR基因座遗传多态性研究

目的 调查11个Y染色体STR基因座的遗传多态性。方法 利用PCR扩增和聚丙烯酰胺凝胶电泳技术对广州地区汉族群体无关男性血样进行11个Y—STR基因座的分型。结果 11个Y—STR基因座在广州地区汉族群体分别发现3～5个等位基因,GD值最低为0.3037(DYS434),最高为0.8455(DYS390)。结论 11个Y—STR基因座在广州地区汉族群体均具有较高的遗传多态性,可应用于法科学个体识别和亲子鉴定。     

Forensic anthropology in the global investigation of humanitarian and human rights abuse: Perspective from the published record

Forensic anthropologists have played key roles in the historical development of forensic science applications to global humanitarian and human rights issues. These anthropological initiatives can be traced back to the Smithsonian seminar organized by T. D. Stewart in 1968 and published in 1970. Key developments include the 1984 delegation sent by the American Association for the Advancement of Science to Argentina and the formation of the Argentine Forensic Anthropology Team. Subsequent highlights include major anthropological involvement in support of investigations by international criminal tribunals, formation of forensic anthropology teams in different countries and activities of the International Commission of Missing Persons and the forensic unit of the International Committee of the Red Cross. Recent developments feature the formation of the Humanitarian and Human Rights Resource Center of the American Academy of Forensic Sciences and its support of worthwhile projects in many countries. The published record provides historical perspective on these developments.