A diagnosis of the primary difference 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 differences between EFM and STRmix™ that are causative of the largest set of likelihood ratio differences. This set of differences is for false donors where there are many instances of LRs just above or below 1 for EFM that give much lower LRs in STRmix™. This is caused by the separate estimation of parameters such as allele height variance and mixture proportion using MLE under H_p and H_a for EFM. This can result in very different estimations of these parameters under H_p and H_a . It results in a departure from calibration for EFM in the region of LRs just above and below 1.