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Population Genetic Issues for Forensic DNA Profiles

NCJ Number
Date Published
November 2017
15 pages
Findings and methodology are reported for a study of the population genetic issues that affect the interpretation of forensic DNA profiles.

Specific project goals were to characterize population structure, interpret lineage marker evidence, and extend a continuous approach. In characterizing population structure, the report notes that the interpretation of matching between DNA profiles of a person of interest and an item of evidence can be done with population genetic models to predict the probability of matching by chance. The calculation of matching probabilities is straightforward if allelic probabilities are known or can be estimated in the relevant population; however, most often the relevant population has not been sampled, and allele frequencies are available only from a broader collection of populations as might be represented in a nation or regional database. In discussing this issue, the report presents results of a worldwide survey of 250 publications that reported allele frequencies at 24 STR loci from 446 populations around the world. Other topics discussed in relation to population structure are SNPs (single nucleotide polymorphisms) and SNVs (single nucleotide variants), as well as relatedness and population structure. Regarding lineage markers, the report discusses Y-STR database analyses and Y-STR profile interpretation. Regarding extending a continuous approach, the report notes that this project has made several advances in the interpretation of STR profiles when they are regarded as being continuous indicators of DNA abundance, in contrast to a binary present/absent call for specific alleles, In discussing a continuous approach, the report discusses low-template DNA, peak height variability, the robustness of results, software validation, and the variability of software results. The report also has a section on "Other Topics," which discusses database matches, DNA interpretation methods, expanded CODIS core, factor of 10, Hd-true testing, and other issues related to population genetics. 35 references

Date Published: November 1, 2017