接触DNA在法医实践中的应用研究进展

人体在接触物体后,会在其表面留下少量接触DNA。对接触DNA的检验是目前法医DNA检验技术的热点和难点。接触DNA的检验成功率差异较大,受各环节多重因素影响。影响接触DNA检验成功率的主要因素有接触DNA检材的准确发现、接触DNA的提取与纯化以及扩增策略的选择和结果分析等。本文详述了接触DNA检验过程的进展及研究展望。     

DNA IQ磁珠法结合Maxwell~（TM） 16自动仪提取接触DNA

目的研究DNA IQ磁珠法结合MaxwellTM 16自动仪对接触DNA提取的应用价值。方法 151份案件接触DNA检材95℃裂解后,采用DNA IQ磁珠法结合MaxwellTM 16自动仪提取DNA,然后进行DNA定量和STR分型检测,统计各种类型的接触DNA含量I、PC CT值和STR分型成功率。结果 151份案件接触DNA检材中,除果核平均DNA获得量为9.51ng以外,其它接触检材的平均DNA获得量均大于10ng,烟蒂检验成功率最高为93%,果核检验成功率较低,为60%。所有DNA样品的IPC CT值均在27左右,纯度高。结论大部分接触DNA检材采用DNA IQ磁珠法结合MaxwellTM 16自动仪可提取到足以进行STR分型的DNA。     

215例枪支上接触DNA检材的检验分析

目的分析215例枪支上接触DNA提取、送检及检验结果,探讨枪支上接触DNA检出情况及可能影响检验结果的影响因素。方法收集自2013年以来受理的215例涉案枪支上接触DNA检材,按照提取部位、检出率、送检时间、检验方法进行分类并对数据进行统计分析。结果215例接触DNA成功检出35例,检出率为16.28%;枪支上不同部位接触检材的检出率无明显差异;硅膜法与改良硅珠法的检出率无明显差异;送检时间早的检材检出率高于送检时间晚的检材并具有统计学意义。结论枪支上接触DNA的检出率与提取部位、送检时间、检验方法等因素有关,日常类似检材应合理提取、及时送检并采取正确检验方法。     

刑事现场188份接触DNA检材法医学检验分析

目的分析188份接触DNA检材的提取、送检和检验结果,探讨接触DNA检出率及可能影响接触DNA检验的因素。方法收集本辖区2016年1月至2016年10月提取并送检的188份接触DNA检材,按照检材载体性质、提取方法、送检时间、检出率等进行分类,采用SPSS13.0软件对数据进行统计分析和χ2检验。结果188份接触DNA检材成功进行STR分型的有38份,检出率为20.21%;其中表面质软、粗糙的载体接触DNA检出率58.82%,高于其它载体接触DNA检出率组的差异具有统计学意义;直接原物提取的接触DNA检材检出率42.11%,高于脱落细胞粘取器提取、棉签拭子转移提取的检出率组的差异具有统计学意义;送检时间早的检材检出率高于送检时间晚的检材组且具有统计学意义。结论接触DNA检材的检出率受载体性质、提取方法、送检时间等因素影响,日常现场勘查时要注重发现检出率高的载体上的接触DNA选择适当的方法提取,并及时送检。     

触摸痕中接触DNA检验概述

接触DNA是指人体与客体相接触后遗留在客体表面的细胞内含有的遗传物质。接触DNA的检验鉴定作为一项较新的技术,在日常工作实践中已被广泛应用。基于接触DNA检验的相关研究在国内外均受到重视,本文借助相关文献,对皮肤触摸痕中接触DNA的形成原理、发现与提取、检验中的影响因素以及对检验结果正确地解读和利用等问题进行阐述,以期为相关研究和应用提供参考和借鉴。     

触摸痕中接触DNA检验概述

接触DNA是指人体与客体相接触后遗留在客体表面的细胞内含有的遗传物质。接触DNA的检验鉴定作为一项较新的技术,在日常工作实践中已被广泛应用。基于接触DNA检验的相关研究在国内外均受到重视,本文借助相关文献,对皮肤触摸痕中接触DNA的形成原理、发现与提取、检验中的影响因素以及对检验结果正确地解读和利用等问题进行阐述,以期为相关研究和应用提供参考和借鉴。     

放置不同时间果核微量生物物证的提取

正近年来,犯罪分子反侦察意识增强,留下的常规生物物证越来越少,DNA检验的主要对象逐渐转变为一些存在形式特殊、类型多样的非常规生物检材,即接触DNA。目前,接触DNA检验是法医DNA检验的难点和热点,其中接触DNA的发现和提取是影响检验成功率的主要因素之一~([1])。本研究将苹果果核在自然环境下放置不同时间,采用擦拭法收集果核不同部位的微量DNA样本,对各样本的STR分型结果进     

Chelex法和两种磁珠法提取接触DNA效果的比较

目的比较Chelex法、DNA IQ磁珠法、EQ国产磁珠法对接触DNA的提取效果。方法将稀释为10ng、100ng的标准品DNA,分别采用Chelex法、DNA IQ磁珠法、EQ国产磁珠法处理;对30例烟蒂和30例牙刷分别采用Chelex法、DNA IQ磁珠法和EQ国产磁珠法提取DNA,然后进行PCR定量和STR检测。结果Chelex法对DNA的提取无损失,DNA IQ磁珠法、EQ国产磁珠法对DNA的提取均有不同程度的损失;烟蒂、牙刷等检材采用Chelex法提取的接触DNA量和IPC CT值显著高于IQ磁珠法、EQ国产磁珠法,但STR检验成功率却低于IQ磁珠法、EQ国产磁珠法。2种磁珠法提取的DNA量、IPC CT值和STR检验成功率无显著性差异。结论污染轻、杂质少的接触DNA检材,用Chelex法提取最为方便快捷;IQ磁珠法、EQ国产磁珠法更适合污染接触DNA检材的提取及自动化操作。     

腐败餐厨油污纸屑上DNA检验1例

接触类生物检材因其DNA含量少、污染严重、PCR抑制物多、DNA检验成功率低一直是法医DNA检验的难点之一[1,2]。特别是餐厨纸屑等非常规接触类生物检材,在气温较高,气候潮湿的环境极易腐败。本文通过对腐败餐厨油污纸屑的DNA检验,得到一男性常染色体和Y染色体DNA结果,经数据比对分析,锁定犯罪嫌疑人,成功助破尘封21年之久命案。     

两种DNA提取方法检测微量陈旧汗斑1例

与人体接触过的衣、物常常附有体表脱落的上皮细胞成分。有试验证明,人体只要接触物体5秒钟以上,即有可能细胞遗留在物体上,也就是说,有可能留下核DNA及线粒体DNA[1]。在刑事案件中,如能成功地对有关物品上粘附的脱落上皮细胞的DNA检验,便可为案件的侦查和审判提供重要的线索和证据[2]。作者在实际检案中遇到一例微量陈旧汗斑,通过联合应用两种DNA的提取方法并进行了对比,解决了该案的难题。报道如下:1简要案情2003年初,某女被杀害。现场提取男士夹克衫一件,领后部有可疑油渍样斑迹,考虑此处有穿衣者留下的汗斑。2检验2.1检验材料犯罪…     

Shedder status—An analysis over time and assessment of various contributing factors

The shedder status of a person is an important consideration when evaluating probabilities of DNA transfer during activity-level assessments. As an extension of our previously published study, the shedder statuses of 38 individuals were reassessed 1 year later. The study found that shedder status may change over time for some individuals and was associated with one's gender, number of items touched, and mobile phone usage. In 29% of touch events, no DNA allele was detected and in 99% of touch events, the amount of DNA deposited was <2 ng. The study also found that in 0.6% of touch events, the participant could be excluded as a contributor of the observed DNA profile, with another person being included. Additionally, our investigations suggest that the current three-category system for shedder status classification may require further refinement to better represent the individuals' shedder status in a population.     

Optimization of the collection and analysis of touch DNA traces

The aim of this work was to optimize a strategy for detection, collection, and analysis of touch DNA traces. 4N6FLOWSwabs™ and cotton swabs were compared by collecting touch DNA traces from glass slides and gun shell casings. Shed cells were visualized using Diamond™ nucleic acid dye and a digital fluorescent microscope. Different collection and extraction methods were tested. Collected samples were amplified with the AmpFlSTR® NGMSElect™ kit and the Precision ID mtDNA Whole Genome Panel.     

Touch DNA Collection Versus Firearm Fingerprinting: Comparing Evidence Production and Identification Outcomes

A project by a metropolitan police agency in 2008–2009 had police use touch DNA kits to collect cell samples from seized firearms. To assess outcomes, results of touch DNA swabbing of firearms were compared to fingerprinting firearm evidence. The rationale was that fingerprinting, as the older technology, was the baseline against which to compare touch DNA. But little is known about ways to measure touch DNA productivity compared to fingerprinting. To examine differences between the two requires comparable measurements. Two measures were used: quantity of probative or investigative evidence produced and identification outcomes. When applied to firearms seized within an Indianapolis, IN police district, touch DNA produced a larger volume of evidence than fingerprinting, but identification outcomes for the two methods were equal. Because touch DNA was deployed by police patrol officers, there are implications for firearm forensics and the choice of forensic approaches used by police.     

Forensic touch DNA recovery from metal surfaces – A review

Trace evidence such as touch (also known as contact) DNA has probative value as a vital forensic investigative tool that can lead to the identification and apprehension of a criminal. While the volume of touch DNA evidence items submitted to forensic laboratories has significantly increased, recovery and amplification of DNA from these items, especially from metal surfaces, remains challenging. Currently little is understood with regards to the underlying mechanisms of metal-DNA interactions in the context of forensic science and how this may impact on DNA recovery. An increased understanding of these mechanisms would allow optimisation of methods to improve outcomes when sampling these materials. This paper reviews the basis of DNA binding to metal substrates, the merits and limitations of current methods and future perspectives of improving recovery and amplification of touch DNA from metal surfaces of forensic interest.     

Efficiency of Casework Direct Kit for extraction of touch DNA samples obtained from cars steering wheels

Analysis of STR profiles obtained from touch DNA has been very useful to the elucidation of crimes. Extraction method may be determinant for the recovery of genetic material collected from different surfaces. Vehicle theft is one of the most common crimes in São Paulo city, Brazil, but collection of biological traces in car steering wheels is not considered, because of the belief that profiles generated won’t be able to identify the thief, only the owner. This study aimed to analyze the efficacy of extraction methods for obtaining DNA profiles in samples collected from steering wheels. Eight criminal acts were simulated with 2 different individuals each (mixture of victim and thief), in duplicate, in order to compare two extraction methods: DNA IQ™ and Casework Direct Kit (both Promega Corporation). Genetic material was collected by double swab method and quantified by Quantifiler™Trio (ThermoFisher Scientific). Amplification was conducted with PowerPlex® Fusion System (Promega). It was possible to obtain STR profiles for all experiments. The mixtures were compared with reference profiles to evaluated how many alleles of each donor were observed. Samples extracted with Casework Direct Kit obtained STR profiles with higher averages of alleles for primary and secondary donors (88.7% and 59.9%, respectively) than those extracted with DNA IQ™ (60.4% and 38.1%, respectively). This could be explained by the differences established in the protocols of both methods, since DNA IQ™ is based on successive washes and can result in loss of DNA, whereas Casework Direct Kit minimizes this problem. We concluded that Casework Direct Kit was more efficient for processing touch DNA samples than DNA IQ™.     

纸张上潜在手印三种前处理方法对DNA检验的影响

目的通过比较常见纸张上潜在手印盲提法与显现后精准提取法的接触DNA检出率,探讨常见纸张上接触DNA前处理的优选方案。方法比较五种常见纸张上使用盲提法和显现潜在手印(茚二酮显现法、茚三酮熏显法)后精准提取法采集的接触DNA样本检出率。结果粗糙日历纸盲提的接触DNA检出率为17.8%,通过茚二酮法和茚三酮法显现的潜在手印所提取的DNA检出率分别为75.6%、77.8%;光滑日历纸三种方法所提取的接触DNA检出率为4.4%、11.1%、11.1%;A4复印纸三种方法接触DNA检出率为20%、37.8%、66.7%;牛皮纸三种方法接触DNA检出率为20%、68.9%、64.4%;快递纸袋的三种方法接触DNA检出率为2.2%、6.7%、46.7%。结论不同纸张上潜在手印经显现后接触DNA检出率不同,通过茚二酮或茚三酮显示潜在手印后精准提取DNA的前处理方法相较于盲提法的接触DNA检出率高。实战中可应用此类方法同时获得手印与DNA分型,以有效提高证据力。     

Persistence of cellular material after exposure to water

Disposing of items of forensic relevance in bodies of water is one countermeasure offenders can use to avoid detection. The impact of immersion in water has been explored for blood, saliva, and semen; however, few studies have assessed touch DNA. Here we report on the effect of exposure to water on the persistence of touch DNA over prolonged periods of time. To evaluate the persistence of cells from touch DNA, after water exposure, three substrates and two water types were tested: plastic, metal, and ceramic, submerged into seawater or tap water. Diamond™ Nucleic Acid Dye was used to stain cells deposited by touch. Cell counts before and after water exposure were compared to investigate cell loss over time, ranging from 6 hours to 5 days. A logarithmic increase in the percent of cells lost was observed over time when the data for substrate and water type conditions were combined. Substrate type influenced the persistence of cells, with the metal substrate retaining cells longer than plastic or ceramic. The influence of water type appeared dependent on the substrate, with varied cell persistence on metal whereas plastic and ceramic recorded similar cell loss over time between water types. The ability to visualize cells after exposure to water could assist in triaging evidence within operational forensic laboratories and allow for targeted sampling. This proof-of-concept study demonstrated that greater than 50% of cells can persist on various items submerged in aqueous environments for at least 5 days, highlighting the possibility for downstream DNA testing.     

96孔过滤板在接触性DNA自动化检验中的应用

目的将96孔过滤板用于自动化工作站,对接触性DNA进行检验。方法收集553份现场提取的附着在烟蒂、饮料瓶、门窗把手、电源网线头、作案工具、手套上的微量接触性生物检材,在96孔过滤板上进行裂解后整体离心,分离载体与裂解液;应用自动化核酸提取纯化仪结合M48磁珠纯化试剂盒提取纯化DNA,采用IdentifilerPlus试剂盒进行扩增,3500XL测序仪电泳分型,ID-X专家系统分析结果。结果在553份检材中,成功获得STR分型的有271份,检验成功率在31.6%~97.3%之间,烟蒂、饮料瓶检材的成功率均在90%以上,提取纯化过程约90min。结论将96孔过滤板用于自动化工作站,可在实现批量接触性DNA的快速、自动化提取的同时,有效提高接触性DNA检出率。