Nucleix Ltd., Tel Aviv 69710, Israel.
Forensic Sci Int Genet. 2010 Feb;4(2):95-103. doi: 10.1016/j.fsigen.2009.06.009. Epub 2009 Jul 16.
Over the past twenty years, DNA analysis has revolutionized forensic science, and has become a dominant tool in law enforcement. Today, DNA evidence is key to the conviction or exoneration of suspects of various types of crime, from theft to rape and murder. However, the disturbing possibility that DNA evidence can be faked has been overlooked. It turns out that standard molecular biology techniques such as PCR, molecular cloning, and recently developed whole genome amplification (WGA), enable anyone with basic equipment and know-how to produce practically unlimited amounts of in vitro synthesized (artificial) DNA with any desired genetic profile. This artificial DNA can then be applied to surfaces of objects or incorporated into genuine human tissues and planted in crime scenes. Here we show that the current forensic procedure fails to distinguish between such samples of blood, saliva, and touched surfaces with artificial DNA, and corresponding samples with in vivo generated (natural) DNA. Furthermore, genotyping of both artificial and natural samples with Profiler Plus((R)) yielded full profiles with no anomalies. In order to effectively deal with this problem, we developed an authentication assay, which distinguishes between natural and artificial DNA based on methylation analysis of a set of genomic loci: in natural DNA, some loci are methylated and others are unmethylated, while in artificial DNA all loci are unmethylated. The assay was tested on natural and artificial samples of blood, saliva, and touched surfaces, with complete success. Adopting an authentication assay for casework samples as part of the forensic procedure is necessary for maintaining the high credibility of DNA evidence in the judiciary system.
在过去的二十年中，DNA 分析彻底改变了法医学，并成为执法的主要工具。如今，DNA 证据是定罪或无罪释放各种类型犯罪嫌疑人的关键，从盗窃到强奸和谋杀。然而，人们忽视了 DNA 证据可能被伪造的令人不安的可能性。事实证明，标准的分子生物学技术，如 PCR、分子克隆，以及最近开发的全基因组扩增 (WGA)，使任何拥有基本设备和技术的人都能够产生具有任何所需遗传特征的大量体外合成（人工）DNA。然后，这种人工 DNA 可以应用于物体表面或掺入真实的人体组织并种植在犯罪现场。在这里，我们表明，目前的法医程序无法区分含有人工 DNA 的血液、唾液和接触表面样本，以及含有体内生成（自然）DNA 的相应样本。此外，使用 Profiler Plus((R)) 对人工和自然样本进行基因分型，得到了没有异常的完整图谱。为了有效应对这个问题，我们开发了一种鉴定检测方法，该方法基于对一组基因组位点的甲基化分析来区分自然和人工 DNA：在自然 DNA 中，一些位点被甲基化，而其他位点未被甲基化，而在人工 DNA 中，所有位点均未被甲基化。该检测方法已在自然和人工血液、唾液和接触表面样本上进行了测试，结果完全成功。在法医程序中对案件样本采用鉴定检测方法是维护司法系统中 DNA 证据高度可信度的必要条件。
