A Comparison of the Model Differences between EuroForMix and STRmix

There is interest in comparing the output, principally the likelihood ratio, from the two probabilistic genotyping software EuroForMix (EFM) and STRmix™. Many of these comparison studies are descriptive and make little or no effort to diagnose the cause of difference. There are fundamental model differences between EFM and STRmix™ that are causative of any likelihood ratio differences. These model differences are easily identified, and it is certainly possible to arbitrate on whether the models in none, one, or both software are the more supported. There is little point in highlighting the output differences without any effort to identify the cause as this can trigger unsubstantiated concern in those cases where a different answer is obtained. In this paper, we further analyse the models within EFM and STRmix™ and explain their differences.