U.S. flag

An official website of the United States government, Department of Justice.

Likelihood Ratio Development for Mixed Y-STR Profiles

NCJ Number
Forensic Science International: Genetics Volume: 35 Dated: July 2018 Pages: 82-96
Date Published
July 2018
15 pages

This research introduced a new likelihood ratio method for evaluating mixed Y-STR profiles that is based on the premise that, given a haplotype has been seen in the person of interest, the most likely source of a second haplotype, matching at all or most loci, is in an individual with a recent common ancestor.


The researchers call the new method the "Haplotype centered" (HC) method for likelihood ratio derivation. For single source, unambiguous haplotypes, the HC method performs identically with the Kappa method proposed by Brenner. Analysis of mixtures requires assignment of a probability to many haplotypes seen neither in the database nor any person typed in the case. A likelihood ratio formula is derived in a way that allows a locus by locus approach. The current research demonstrates the application of the HC method on a series of Y-STR mixtures originating from two to four individuals in a manner that is still calculated locus-by-locus in nature. (publisher abstract modified)

Date Published: July 1, 2018