Likelihood Models for Forensic Genealogy

2020/10/06 by William H. Press, Press, William H., John Hawkins +1
Biochemistry, Genetics and Molecular Biology · Computer Science · #Bayesian Methods and Mixture Models #FOS: Biological sciences #Forensic and Genetic Research #Genomics (q-bio.GN)

paper · pdf · doi:10.48550/arxiv.2010.02985

openalex publication_date 2020/10/06 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

In the idealized Morgan model of crossover, we study the probability distributions of shared DNA (identical by descent) between individuals having a wide range of relationships (not just lineal descendants), especially cases for which previous work produces inaccurate results. Using Monte Carlo simulation, we show that a particular, complicated functional form with just one continuous fitted parameter accurately approximates the distributions in all cases tried. Analysis of that functional form shows that it is close to a normal distribution, not in shared fraction f, but in the square-root of f. We describe a multivariate normal model in this variable for use as a practical framework for several general tasks in forensic genealogy that are currently done by less-accurate and less well-founded methods.

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