Identification of Individuals in a DNA Mixture Using SNP Markers

Abstract

This article focuses mainly on DNA mixture from two contributors, a victim and an unknown culprit. There are two areas I believe will be of interest to forensic scientists, police and a Jury. These areas are identification of an individual in a DNA mixture and familial DNA database searching of a culprit through a relative. In this article, I looked at identification of individuals in a mixture using Single Nucleotide Polymorphisms (SNPs) markers. SNPs are starting to be used for forensic identification; I employed them as they produce incredible results for identification in a two-person mixture. The conservative method I employed here is the random man not excluded probability – P (RMNE) approach, an inclusion probability method generally considered as a frequentist approach. It was found that an optimum allele frequency of 0.2 is required to produce almost certain identification with much distortion in identifying an individual even when inbreeding is up to 50% in a population. Another interesting thing is that relatives of a suspect whom are actual contributors to the DNA mixture can also be identified. In a case where there are relatives in the mixture it was found that twice the number of SNP panels is required to identify an individual than in a case where no relative is involved. And lastly, typing more SNP panels helps to improve identification and therefore produce forensically useful results.