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STRmix (TM) collaborative exercise on DNA mixture interpretation

NCJ Number
Forensic Science International-Genetics Volume: 40 Dated: May 2019 Pages: 1-8
Date Published
May 2019
8 pages
This article reports on an intra and inter-laboratory study (174 participants) that used the probabilistic genotyping (PG) software STRmix in analyzing two complex mixtures from the PROVEDIt set, analyzed on an Applied Biosystems 3500 Series Genetic Analyzer.

For Sample 1 (low template, in the order of 200 rfu for major contributors) five participants described the comparison as inconclusive with respect to the POI or excluded him. Where LRs were assigned, the point estimates ranging from 210 4 to 810 6. For Sample 2 (in the order of 2000 rfu for major contributors), LRs ranged from 210 28 to 210 29. Where LRs were calculated, the differences between participants can be attributed to (from largest to smallest impact): 1) varying number of contributors (NoC); 2) the exclusion of some loci within the interpretation; 3) run-to-run variation due to the random sampling inherent to all MCMC-based methods; and 4) differences in local CE data analysis methods leading to variation in the peaks present and their heights in the input files used. This study demonstrates a high level of repeatability and reproducibility among the participants. For those results that differed from the mode, the differences in LR were almost always minor or conservative. (publisher abstract modified)

Date Published: May 1, 2019