Trace DNA Sampling Success from Evidence Items Commonly Encountered in Forensic Casework

Trace DNA analysis is a significant part of a forensic laboratory's workload. Knowing optimal sampling strategies and item success rates for particular item types can assist in evidence selection and examination processes and shorten turnaround times. In this study, forensic short tandem repeat (STR) casework results were reviewed to determine how often STR profiles suitable for comparison were obtained from “handler” and “wearer” areas of 764 items commonly submitted for examination. One hundred and fifty‐five (155) items obtained from volunteers were also sampled. Items were analyzed for best sampling location and strategy. For casework items, headwear and gloves provided the highest success rates. Experimentally, eyeglasses and earphones, T‐shirts, fabric gloves and watches provided the highest success rates. Eyeglasses and latex gloves provided optimal results if the entire surfaces were swabbed. In general, at least 10%, and up to 88% of all trace DNA analyses resulted in suitable STR profiles for comparison.     

Discrimination of Geographical Origin of Asian Garlic Using Isotopic and Chemical Datasets under Stepwise Principal Component Analysis

Isotopic compositions of δ²H, δ¹⁸O, δ¹³C, and δ¹⁵N and concentrations of 22 trace elements from garlic samples were analyzed and processed with stepwise principal component analysis (PCA) to discriminate garlic's country of origin among Asian regions including South Korea, Vietnam, Taiwan, and China. Results indicate that there is no single trace‐element concentration or isotopic composition that can accomplish the study's purpose and the stepwise PCA approach proposed does allow for discrimination between countries on a regional basis. Sequentially, Step‐1 PCA distinguishes garlic's country of origin among Taiwanese, South Korean, and Vietnamese samples; Step‐2 PCA discriminates Chinese garlic from South Korean garlic; and Step‐3 and Step‐4 PCA, Chinese garlic from Vietnamese garlic. In model tests, countries of origin of all audit samples were correctly discriminated by stepwise PCA. Consequently, this study demonstrates that stepwise PCA as applied is a simple and effective approach to discriminating country of origin among Asian garlics.     

磁珠DNA自动提取系统在法医检验中的应用

磁珠DNA自动提取系统是将磁珠分离技术与DNA自动提取工作站结合运用,以达到高效提取DNA的目的,它具有操作时间短、准确性高、检材用量少等特点,特别适用于大批量生物检材的快速提取,是目前主流的DNA自动化提取方法。本文对磁珠DNA自动提取系统的基本组成、工作原理、操作流程及其在法医检验领域中的应用等进行了综述,并对该系统的发展前景进行了展望。     

系统检验方法在可疑文件鉴定中运用

通过对近年来成功解决的几起可疑文件鉴定的典型案例分析,较详细地阐述在文件鉴定实践中,如何运用系统检验的思想,通过可疑文件上留下的细微变造痕迹,巧妙识别可疑文件的伪造手段和方法,为法庭提供科学、可信的证据,取信于法官、律师及当事人,使得案件最终圆满审结.在面对某些疑难案件的鉴定中,在鉴定思路和方法上对文件检验人员,有一定的启示作用.     

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.     

Potential forensic application of closely linked autosomal STR haplotype in complex kinship testing

It has been noticed that the most commonly used commercial STR kits and mtDNA may not be able to solve some special kinship cases, such as alleged aunt, uncle, niece, nephew or half-siblings. Due to its unique hereditary pattern, the haplotype of genetic markers could be a solution of these questioned family relationships. In this study, we investigated the genetic features of an autosomal STR cluster by employing confirmed family samples. To evaluate the forensic practical value of autosomal STR haplotype, 5 closely linked STR loci, D1S2127-D1S2138-D1S3460-D1S1643-D1S518, which were arranged in about 2 cM region (from 186.29 cM to 188.02 cM; 1 cM represents 1% average recombination between two loci) on chromosome one, were selected to compose haplotype. Genotyping of 60 samples from 8 trios (father–mother–children), 8 duos (father or mother–children), and 4 three-generation pedigrees were performed using PAGE. Haplotypes were identified in the child by determining alleles for all 5 loci transmitted from each parent. Total 73 haplotypes were detected in all samples and 34 haplotypes were observed to be passed down as a whole and was corresponding with the inherited characteristics of haplotype. In all family members, 34 unrelated individuals contributed 65 haplotypes, of which 62 haplotypes appeared only once and the rest 3 haplotypes appeared twice. No recombination was observed in 4 three-generation pedigrees. In conclusion, the haplotype consisting of 5 closely linked autosomal STRs could pass down steadily as a whole. The family specificity of most haplotypes may provide a unique advantage in forensic complex kinship testing.     

A New Method for the Removal and Analysis of Small Particles Adhering to Carpet Fiber Surfaces,,

Fibers are a commonly encountered evidence type and fiber comparisons are routinely conducted. When the characteristics of questioned and known fibers correspond, the probative value is limited because the characteristics compared are determined by their manufacture. It would be valuable to test the hypothesis that questioned fibers originated from a specific carpet. One means of testing this is to analyze fine particles on the fibers. A procedure was developed for removing adhering particles from fibers and preparing them for scanning electron microscopy/ energy dispersive X‐ray spectrometry (SEM/EDS) analysis. The efficacy of several fluids (acetone, ethanol, hexanes, aqueous ethanol, aqueous sodium hexametaphosphate) and agitation methods (sonication and vortexing) for removing particles from fibers was evaluated. The most effective method evaluated was sonication in ethanol for 10 min. The recovered particles were filtered onto a polycarbonate filter and analyzed by automated SEM/EDS analysis to generate data on the particle assemblage. This method makes possible future research to test the within‐item and between‐item variability of particle assemblages on fibers.     

Analysis and Discrimination of Single‐Layer White Architectural Paint Samples,

Comparative analyses of 50 single‐layer white architectural paints were conducted to determine the discrimination power using standard techniques and to provide a basis for assessing significance when paints with limited features are not discriminated. Utilizing Fourier transform infrared spectroscopy (FTIR), 68 undifferentiated pairs resulted, yielding a discrimination of 94.45%. Adding stereomicroscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and backscatter electron (BSE) imaging, and pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS), the overall discrimination was 99.35%. The study included blind verification replicates, which resulted in the only pairs without indications of physical or chemical differences. The remaining groups of undifferentiated samples contained subtle differences by at least one technique, but were considered undifferentiated for the discrimination power evaluations. This study demonstrates a high degree of discrimination of single‐layer white architectural paints using methods of analysis often encountered in forensic science laboratories.     

《特殊痕迹检验》课程考核模式的改革与实践

考核模式改革是我校＂教学重心转变＂工作中教学模式改革的重点和核心内容之一。本文通过对《特殊痕迹检验》课程考核模式的改革与实践,提出了适应本专业学生教学练战一体化的考核模式。     

实案测试中被测试对象心理状态探析

心理学的研究离不开各种实验,心理测试技术(俗称"测谎"技术)实际上就是心理学实验方法的一种。此项技术在我国的研究应用已经30多年,辅助司法领域进行了大量的实案心理测试①。不仅对陷入侦破困境的案件起到很大作用,也对心理学在实战领域的应用研究提供了一种实验范式。对进行心理测试案件的研究发现,很多的变量都会影响到测试的结果,进而影响测试效度。被测人②的心理状态是其中很重要但是很容易被忽视的因素之一,这是一个非常值得关注研究的领域,不仅关系到心理测试技术的发展,也关系到司法领域人权和司法公正问题。