In this paper, the authors provide examples where the likelihood ratio for DNA interpretation models may be easily obtained to help with the internal validation of probabilistic software, through the use of three software packages; they also provide profiles and equations so the calculations may be replicated or applied to different software.
There has been a recent push from many jurisdictions for the standardization of forensic DNA interpretation methods. Current research is moving from threshold-based interpretation strategies towards continuous interpretation strategies. However, laboratory uptake of software employing probabilistic models is slow. Some of this reluctance could be due to the perceived intimidating calculations to replicate the software answers and the lack of formal internal validation requirements for interpretation software. In this paper, the authors describe a set of experiments which may be used to internally validate in part probabilistic interpretation software. These experiments included both single source and mixed profiles calculated with and without dropout and drop-in and studies to determine the reproducibility of the software with replicate analyses. The authors do this by way of example using three software packages: STRmix™, LRmix, and Lab Retriever. They outline and demonstrate the profile examples where the expected answer may be calculated and provide all calculations. (Publisher Abstract Provided)