以前有人主张从犯罪现场DNA预测不明嫌犯的出现,在法医DNA表型(FDP)的背景下,主要适用于单一来源的DNA样本,而来自不止一个人贡献的DNA混合物的FDP,被视为具有挑战性。有了这个谋杀案的报告,我们实际上证明了从混合犯罪现场痕迹中预测未知嫌疑人的外观DNA的可行性,不明嫌犯和已知受害者对此做出了贡献。从这个两人的DNA混合物中,我们成功地预测了眼睛,通过应用靶向大规模平行测序(MPS),使用HIrisPlex-S系统对不明嫌犯的头发和肤色进行检测。我们认为,至少有三个因素有利于混合犯罪现场痕迹对未知嫌疑人的外观DNA预测,在这个谋杀案中遇到的问题:i)来自混合物中两个人中的一个(这里是已知的受害者)的参考DNA分析的SNP基因型知识,ii)两个捐助者对混合犯罪现场污点的DNA贡献大约相等,和iii)允许定量SNP分析的MPS的使用。此外,我们表明,在这个混合犯罪现场痕迹中额外分析动物DNA提供了进一步的调查信息。我们设想我们在这里用于分析谋杀案中两人混合犯罪现场痕迹的DNA调查策略,未来将适用于更多两人DNA混合的刑事案件,例如性侵犯案件。
It has been advocated before that appearance prediction of unknown suspects from crime scene DNA, in the context of Forensic DNA Phenotyping (FDP), is mostly suitable for single source DNA samples, whereas FDP from DNA mixtures to which more than one person contributed, is viewed challenging. With this report on a murder
case, we practically demonstrate the feasibility of appearance DNA prediction of an unknown suspect from a mixed crime scene trace, to which the unknown suspect and the known victim had contributed. From this two-person DNA mixture, we successfully predicted eye, hair and skin color of the unknown suspect with the HIrisPlex-S system by applying targeted massively parallel sequencing (MPS). We argue that at least three factors benefit appearance DNA prediction of unknown suspects from mixed crime scene traces, which were met in this murder
case: i) SNP genotype knowledge from reference DNA analysis for one of the two persons in the mixture (here the known victim), ii) about equal DNA contributions by both donors to the mixed crime scene stain, and iii) the use of MPS allowing quantitative SNP analysis. Moreover, we show that additionally analyzing animal DNA in this mixed crime scene trace provides further investigative information. We envision that the investigative DNA strategy that we applied here for analyzing a two-person mixed crime scene trace in a murder
case, will be applied in the future to more criminal cases with two-person DNA mixtures, for instance sexual assault cases.