Preprint: Elston–Stewart algorithm applied to exact Y-STR match probability calculation in pedigree forensics

A preprint posted to bioRxiv on 19 August 2026 by researchers at Cold Spring Harbor Laboratory describes the application of the Elston–Stewart algorithm — a classical method from quantitative genetics for computing likelihoods across pedigrees — to the problem of calculating exact match probabilities for Y-chromosomal short tandem repeat (Y-STR) profiles in forensic genetics contexts.

Y-STR analysis is widely used in forensic casework, particularly in sexual offence investigations, because the non-recombining nature of the Y chromosome means that male-line relatives share the same Y-STR haplotype. This creates a statistical challenge: under the defence hypothesis that a suspect was not the trace donor, calculating the probability that another man in the relevant suspect population would share the same Y-STR profile requires modelling of relatedness and population structure. The Elston–Stewart algorithm, by enabling efficient traversal of pedigree structures, offers a mathematically tractable approach to this calculation.

The preprint is directly relevant to researchers in forensic genetics, population genetics, and statistical genetics, as well as to those working on pedigree-based probability methods more broadly. The Elston–Stewart algorithm is also of interest to the Evagene research community given its application to pedigree likelihood computation.

This is a preprint and has not yet been peer-reviewed.