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The Variability in Likelihood Ratios due to Different Mechanisms

NCJ Number
Forensic Science International - Genetics Volume: 14 Dated: January 2015 Pages: 187-190
Date Published
January 2015
4 pages

This study explored the size of the Markov chain Monte Carlo techniques (MCMC) variability within the interpretation software STRmix compared to other sources of variability in forensic DNA profiling, including PCR, capillary electrophoresis load and injection, and the makeup of allele frequency databases.


The MCMC variability within STRmix was shown to be the smallest source of variability in this process. Recently there has been a drive towards standardization of forensic DNA interpretation methods resulting in the uptake of probabilistic interpretation software. Some of these software solutions use MCMC. They will not produce an identical answer after repeat interpretations of the same evidence profile because of the Monte Carlo aspect. This is a new source of variability within the forensic DNA analysis process. (Publisher abstract modified)

Date Published: January 1, 2015