KLINK: A program for kinship testing with pairwise linked STR markers

We present KLINK, a free, user-friendly tool for forensic kinship testing that accommodates linkage between marker pairs and also advanced mutation models. This addresses a gap in existing software, which typically handles either linkage or mutation modelling, but not both. In realistic simulations with up to 43 markers, our method captured nearly all linkage-related effects on the likelihood ratio, whereas ignoring linkage often resulted in substantial LR bias and reduced power to identify the correct relationship. The results indicate that KLINK is well suited for forensic kinship casework, both with standard kits of about 20 markers and with extended kits used in more challenging cases. The program is available both as a web application and as an R package, and does not require programming skills. Finally, as a separate companion to KLINK, we developed the interactive app Linkage Lab, for exploring LR behaviour and building intuition in kinship analysis with linked markers.