Forensic Ancestry Inference: Data Requirements, Analysis Methods, and Interpretation of Results

Abstract

Being able to determine the biogeographic ancestry of an individual has been important in many forensic efforts to determine the identity of a partial or decayed body. Now a DNA sample can be the forensic equivalent of an unidentified individual using just some blood left at the scene of a crime or some semen left from a rape. The standard DNA markers, short tandem repeats, used globally to tie an individual to the crime scene DNA, are not good for inferring biogeographic ancestry because they do not vary much among populations. But they do vary greatly among individuals - every population has many alleles at each locus, but it is the same “many” in most populations. Single nucleotide polymorphisms (SNPs), on the other hand, can vary greatly in their frequencies among populations. Recent efforts by many researchers have begun to provide those markers. Panels of Ancestry Informative SNPs (AISNPs) have been developed by many researchers. These have been shown to vary in frequency among populations. Databases have been developed for estimating how likely it is for a DNA profile for those SNPs to occur in the different populations. Data requirements, analytic methods, and criteria for interpreting the results are all discussed.