Implication of population structure in the resolution of cattle stealing cases

Estimation of population subdivision using genetic markers shows that genetic differentiation in livestock and pet breeds is significantly higher than in human populations. Nevertheless, the influence of population substructure and sample size on match probability has not been extensively analyzed in domestic species. To evaluate the magnitude of the subpopulation effect on estimation of match probabilities in bovine robbery cases, we calculated and compared the match probabilities obtained from cattle breed databases using both real, adjudicated cases from the Buenos Aires Province (Argentina), as well as simulated data. While the Balding and Nichols' correction, when applied to the population database used in the case, produce a more conservative value favorable to the defendant, the match probabilities calculated using the simple product estimator produce a value favorable to the prosecution. We suggest an alternative procedure that can be used. The method consists of choosing the highest value from all match probabilities calculated from the database of each breed. This approach represents an intermediate and more accurate estimation of match probability, although it still produces a slight conservative value favorable to the defense.