The Ge.F.I. DNA Proficiency Test: Year-one experience

The Ge.F.I. (the Italian Speaking Working Group of ISFG) has launched the first DNA Proficiency Test in 2012. The aim is to increase the external quality controls in forensic genetics in Italy and to drive to the standardizations of methods within the laboratories. Reference and mixed stains typing as well as statistical exercises were proposed and 26 laboratories submitted results.     

Murder in south London: a novel use of DNA profiling.

Lorraine Benson's body was found beaten and strangled at Raynes Park, Surrey, in December 1988. Considering the possibility of linked offences, a murder squad was set up to work alongside a team already investigating a rape series in the Kingston area. A man's handkerchief left at a site a quarter of a mile from the murder scene was found to be stained with blood and saliva matching that of the victim. A DNA profile was obtained from a stain of nasal mucus on this handkerchief and found to match a suspect later arrested for an attempted rape in the same locality. Also of forensic interest were dust marks made by the zips of the victim's and defendant's coats and identification of the rope used for strangulation.     

Genetic markers in human bone: I. Deoxyribonucleic acid (DNA) analysis.

Deoxyribonucleic acid (DNA) was isolated from a number of spongy and compact human bone tissue specimens, and the yield was estimated on a "per milligram of starting tissue" basis. DNA was, in addition, isolated from a number of corresponding blood and bone tissue specimens. Spectrophotofluorometry and ethidium bromide visualization on minigels were used to estimate the quantity and degree of degradation of DNA. The DNA from several blood-bone pairs is shown to give concordant restriction fragment length polymorphism (RFLP) typing results by two different typing protocols with five different single-locus probes. DNA from several additional blood-bone pairs is shown to give concordant results for human leucocyte antigen (HLA)-DQ alpha phenotypes following polymerase chain reaction (PCR) amplification and hybridization to specific allele-specific oligonucleotide (ASO) probes, and for the variable numbers of tandem repeats (VNTR) length polymorphisms 3' to the human apolipoprotein B (APOB) gene following PCR amplification with specific primers and analysis of the products by electrophoresis and ethidium bromide visualization.     

PCR DNA typing of stamps: evaluation of the DNA extraction

Today, the PCR analysis of DNA from the saliva deposited on a stamp of an anonymous letter can lead to an identification. However, this analysis still involves problems, and DNA extraction can be particularly difficult. A comparative study of two DNA extraction methods with two categories of postage stamps was carried out and a purification process was tested. This study shows that the extraction with phenol/chloroform gives much better results than Chelex extraction. A purification process such as the use of Centricon^TM 100 microconcentrators is recommended when an inhibition of PCR is present. This operation, however, results in a large loss of material.     

Recombinant DNA research: actions under the guidelines--NIH. Notice of actions under NIH guidelines for research involving recombinant DNA molecules

This notice sets forth actions taken by the Director, National Institute of Allergy and infectious Diseases (NIAID), by authority of the Director. NIH, under the June 1983 NIH Guidelines for Research Involving Recombinant DNA Molecules (48 FR 24556).     

国际刑警组织DNA技术的应用和数据交换

国际刑警组织为了对各成员国的DNA检验工作提供技术支持 ,促进DNA技术的广泛应用 ,设立了DNA组。DNA专家组是DNA组的主要咨询机构 ,负责推荐DNA采样和证据采集、DNA数据库、质量控制、DNA技术培训等方面的指导原则。国际刑警组织还定期召开国际DNA用户大会 ,开展地区性DNA技术培训 ,以促进DNA技术的普及、应用和发展。本文主要介绍国际刑警组织在DNA技术方面开展的工作及推荐的一些指导原则。     

Visualising DNA transfer: Latent DNA detection using Diamond Dye

A central question is ‘how did DNA get there’? To help answer this, we visually monitored and recorded DNA transfer from one substrate to another. When an individual touches a substrate, traces of their DNA are transferred (primary/direct) which can then subsequently be transferred to a second substrate (secondary/indirect). Currently DNA transfer and how much remains can only be determined by collecting the biological material from the substrate, isolating the DNA and quantifying the amount recovered. However, Diamond™ Dye (DD) enables such DNA transfer events to be visualised by monitoring the movement of cellular material.We examined primary and secondary DNA transfer using aluminium as a primary substrate with cotton, polyester, aluminium and plastic as secondary substrates and four contact types between two substrates (passive, pressure, friction and friction with pressure). Participants pressed their index finger against the aluminium for 15 s and then DD was applied to the area of contact; cellular material was detected via a fluorescence microscope. Contact between that substrate and a second substrate was performed, using one of the four contact types. After this contact between substrates each was viewed microscopically and transfer of cellular material was recorded.Cellular material could be recorded as having transferred from one substrate to another. Substrate and contact type had an effect on the extent DNA transfers. DNA transferred at a high rate with aluminium as a primary substrate and cotton, polyester and aluminium as secondary substrates when pressure with friction was applied. This information expands our understanding of how DNA transfers and which factors affect it, thus assisting greatly with activity level reporting as to how DNA came to be where it was found.     

微量体表脱落上皮细胞的DNA检验

目的　建立微量体表脱落上皮细胞的DNA检验方法。　方法　采用Chelex -10 0法提取DNA ,以Microcon -10 0纯化柱纯化浓缩DNA ,用ProfilerPlus试剂盒PCR扩增后用 3 10基因分析仪检测。　结果　 10种常见粘附有体表脱落上皮细胞的样本 10 0个 ,其中 7种 70个样本成功检测到 10个STR位点的分型 ,检出率为 10 0 % ,其余 3种样本检出率分别为 5 0 %、2 0 %、10 % ,将该方法应用于 2例实际检案 ,取得满意效果。　结论　所建立方法稳定可靠 ,易于操作 ,适用于多种检材 ,为微量体表脱落上皮细胞的DNA检验提供了确实可行的检验方法     

美国定罪后DNA检测立法评析

随着错案披露数量的增加,DNA检测的作用得到进一步证实.美国各州意识到必须进行定罪后DNA检测立法.司法部采取了相关的调研,随后,立法活动在各州全面展开,2004年<无辜者保护法案>的制定标志着立法进入成熟阶段.在此过程中,涉及对检测动议申请权的宪法属性探讨,律师帮助权以及法官看守职责的分析.迄今为止,立法DNA检测取得较好的效果.研究这一立法历程及其理论争议,既可以了解近十年的法律变革,也有利于我国法治建设的完善.     

Estimating allele frequencies of hypervariable DNA systems.

Several polymorphisms of human DNA have been shown to be hypervariable due to the recurrence of a variable number of tandem repeats (VNTRs) in the lengths of allelic restriction fragments. The recurrence of allelic variants in this novel class of polymorphisms seems to comply well with a model of continuous random variables. Based on this assumption, we have compiled some simple algorithms for classification of continuous data and estimation of classes of relative frequencies and have implemented these routines for the management of databases storing hypervariable single locus DNA genetic systems. The algorithms are compiled in BASIC language and can be incorporated in task-oriented computer programs. Three procedures are discussed, based in turn on: (a) using predetermined, arbitrary classes; (b) point estimations of frequencies for single fragments using error measurements associated with the kilobase value assignment; (c) estimates of phenotype frequencies according to error measurements. Error measurements are obtained from a statistic of values pertaining to several restriction fragments (genomic controls) repeatedly tested in different experiments. Problems related to these approaches are discussed.     

Linear mixture analysis: a mathematical approach to resolving mixed DNA samples.

With the advent of PCR-based STR typing systems, mixed samples can be separated into their individual DNA profiles. Quantitative peak information can help in this analysis. However, despite such advances, forensic mixture analysis still remains a laborious art, with the high cost and effort often precluding timely reporting. We introduce here a new automated approach to resolving forensic DNA mixtures. Our linear mixture analysis (LMA) is a straightforward mathematical approach that can integrate all the quantitative PCR data into a single rapid computation. LMA has application to diverse mixture problems. As demonstrated here on laboratory STR data, LMA can assess the quality and utility of its solutions. Such rapid and robust methods for computer-based analysis of DNA mixtures may help in reducing crime.     

Use of DNA profiles for investigation using a simulated national DNA database: Part II. Statistical and ethical considerations on familial searching

Familial searching consists of searching for a full profile left at a crime scene in a National DNA Database (NDNAD). In this paper we are interested in the circumstance where no full match is returned, but a partial match is found between a database member's profile and the crime stain. Because close relatives share more of their DNA than unrelated persons, this partial match may indicate that the crime stain was left by a close relative of the person with whom the partial match was found. This approach has successfully solved important crimes in the UK and the USA. In a previous paper, a model, which takes into account substructure and siblings, was used to simulate a NDNAD [1]. In this paper, we have used this model to test the usefulness of familial searching and offer guidelines for pre-assessment of the cases based on the likelihood ratio. Siblings of “persons” present in the simulated Swiss NDNAD were created. These profiles (N = 10,000) were used as traces and were then compared to the whole database (N = 100,000). The statistical results obtained show that the technique has great potential confirming the findings of previous studies. However, effectiveness of the technique is only one part of the story. Familial searching has juridical and ethical aspects that should not be ignored. In Switzerland for example, there are no specific guidelines to the legality or otherwise of familial searching. This article both presents statistical results, and addresses criminological and civil liberties aspects to take into account risks and benefits of familial searching.     

FaSTR DNA: A new expert system for forensic DNA analysis

The automation of DNA profile analysis of reference and crime samples continues to gain pace driven in part by a realisation by the criminal justice system of the positive impact DNA technology can have in aiding in the solution of crime and the apprehension of suspects. Expert systems to automate the profile analysis component of the process are beginning to be developed. In this paper, we report the validation of a new expert system FaSTR DNA, an expert system suitable for the analysis of DNA profiles from single source reference samples and from crime samples. We compare the performance of FaSTR DNA with that of other equivalent systems, GeneMapper™ ID v3.2 (Applied Biosystems, Foster City, CA) and FSS-i³ v4 (The Forensic Science Service^® DNA expert System Suite FSS-i³, Forensic Science Service, Birmingham, UK) with GeneScan^® Analysis v3.7/Genotyper^® v3.7 software (Applied Biosystems, Foster City, CA, USA) with manual review. We have shown that FaSTR DNA provides an alternative solution to automating DNA profile analysis and is appropriate for implementation into forensic laboratories. The FaSTR DNA system was demonstrated to be comparable in performance to that of GeneMapper™ ID v3.2 and superior to that of FSS-i³ v4 for the analysis of DNA profiles from crime samples.     

The decision theory of paternity disputes: optimization considerations applied to multilocus DNA fingerprinting.

The solution of paternity disputes using results from scientific analyses is studied from a decision-theoretical viewpoint. Two alternative approaches to decision making, the so-called 'Bayes' and 'Minimax' strategies, are described and discussed. If prior probabilities of paternity are exactly known, then Bayes decisions are (a) independent of the source of evidence and (b) optimal with respect to average losses caused by wrong decisions. However, it is concluded that Minimax decisions, which depend upon the employed test system but not upon prior probabilities, are more appropriate in paternity cases if equal prior good will towards disclaimed children and alleged fathers is demanded. It is further demonstrated that, when major evidence about paternity comes from multilocus DNA fingerprinting, prior probabilities must be known quite accurately for Bayes decisions to be superior with respect to average losses. Finally, we are able to show that 'quasi' Bayes decision making, that is, adopting a neutral prior probability of 0.5 but leaving thresholds for decision making unchanged, coincides with Minimax decision making if multilocus DNA fingerprinting is employed.     

Interpreting DNA mixtures in structured populations.

DNA profiles from multiple-contributor samples are interpreted by comparing the probabilities of the profiles under alternative propositions. The propositions may specify some known contributors to the sample and may also specify a number of unknown contributors. The probability of the alleles carried by the set of people, known or unknown, depends on the allelic frequencies and also upon any relationships among the people. Membership of the same subpopulation implies a relationship from a shared evolutionary history, and this effect has been incorporated into the probabilities. This acknowledgment of the effects of population structure requires account to be taken of all people in a subpopulation who are typed, whether or not they contributed to the sample.