US Army Criminal Investigation Laboratory (USACIL), 4930 N 31st Street, Forest Park, GA, 30297.
Institute of Environmental Science and Research Limited, Private Bag 92021, Auckland, 1142, New Zealand.
J Forensic Sci. 2020 Jul;65(4):1072-1084. doi: 10.1111/1556-4029.14306. Epub 2020 Mar 5.
The reporting of a likelihood ratio (LR) calculated from probabilistic genotyping software has become more popular since 2015 and has allowed for the use of more complex mixtures at court. The meaning of "inconclusive" LRs and how to communicate the significance of low LRs at court is now important. We present a method here using the distribution of LRs obtained from nondonors. The nondonor distribution is useful for examining calibration and discrimination for profiles that have produced LRs less than about 10 . In this paper, a range of mixed DNA profiles of varying quantity were constructed and the LR distribution considering the minor contributor for a number of nondonors was compared to the expectation given a calibrated system. It is demonstrated that conditioning genotypes should be used where reasonable given the background information to decrease the rate of nondonor LRs above 1. In all 17 cases examined, the LR for the minor donor was higher than the nondonor LRs, and in 12 of the 17 cases, the 99.9 percentile of the nondonor distribution was lower when appropriate conditioning information was used. The output of the tool is a graph that can show the position of the LR for the person of interest set against the nondonor LR distribution. This may assist communication between scientists and the court.
自 2015 年以来，报告来自概率基因分型软件计算的似然比（LR）变得更加流行，并且允许在法庭上使用更复杂的混合物。现在，“不确定”LR 的含义以及如何在法庭上传达低 LR 的意义非常重要。我们在这里提出了一种使用非供体获得的 LR 分布的方法。非供体分布对于检查校准和对产生小于约 10 的 LR 的配置文件的区分很有用。在本文中，构建了一系列不同数量的混合 DNA 配置文件，并将考虑次要贡献者的许多非供体的 LR 分布与校准系统给出的预期进行了比较。结果表明，应该在合理的情况下使用条件基因型，以降低高于 1 的非供体 LR 率。在所检查的 17 个案例中，次要供体的 LR 均高于非供体的 LR，在适当使用条件信息的情况下，17 个案例中有 12 个案例的非供体分布的 99.9 百分位数较低。该工具的输出是一个图形，可以显示感兴趣人员的 LR 相对于非供体 LR 分布的位置。这可能有助于科学家和法庭之间的沟通。
