Andersen Mikkel Meyer, Eriksen Poul Svante, Morling Niels
Department of Mathematical Sciences, Aalborg University, DK-9220 Aalborg, Denmark; Section of Forensic Genetics, Department of Forensic Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2100 Copenhagen, Denmark.
Department of Mathematical Sciences, Aalborg University, DK-9220 Aalborg, Denmark.
Forensic Sci Int Genet. 2023 May;64:102839. doi: 10.1016/j.fsigen.2023.102839. Epub 2023 Jan 30.
The discrete Laplace method is recommended by multiple parties (including the International Society for Forensic Genetics, ISFG) to estimate the weight of evidence in criminal cases when a suspect's Y-STR profile matches the crime scene Y-STR profile. Unfortunately, modelling the distribution of Y-STR profiles in the population reference database is time-consuming and requires expert knowledge. When the suspect's Y-STR profile is added to the database, as would be the protocol in many cases, the parameters of the discrete Laplace model must be re-estimated. We found that the likelihood ratios with and without adding the suspect's Y-STR profile were almost identical with 1,000 or more Y-STR profiles in the database for Y-STR profiles with 8, 12, and 17 loci. Thus, likelihood ratio calculations can be performed in seconds if an established discrete Laplace model based on at least 1,000 Y-STR profiles is used. A match in a population reference database with 17 Y-STR loci from at least 1,000 male individuals results in a likelihood ratio above 10,000 in approximately 94% of the cases, and above 100,000 in approximately 82% of the cases. We offer free software accessible without restrictions to estimate a discrete Laplace model using a Y-STR reference database and subsequently to calculate likelihood ratios.
当嫌疑人的Y-STR图谱与犯罪现场的Y-STR图谱匹配时，多方（包括国际法医遗传学协会，ISFG）推荐使用离散拉普拉斯方法来评估刑事案件中的证据权重。不幸的是，对群体参考数据库中Y-STR图谱的分布进行建模既耗时又需要专业知识。当像许多情况下的协议那样将嫌疑人的Y-STR图谱添加到数据库中时，必须重新估计离散拉普拉斯模型的参数。我们发现，对于具有8、12和17个基因座的Y-STR图谱，数据库中有1000个或更多Y-STR图谱时，添加和不添加嫌疑人Y-STR图谱时的似然比几乎相同。因此，如果使用基于至少1000个Y-STR图谱建立的离散拉普拉斯模型，似然比计算可以在几秒钟内完成。在一个来自至少1000名男性个体的具有17个Y-STR基因座的群体参考数据库中，匹配结果在大约94%的情况下会产生高于10000的似然比，在大约82%的情况下会产生高于100000的似然比。我们提供免费软件，可无限制访问，用于使用Y-STR参考数据库估计离散拉普拉斯模型，随后计算似然比。
