In 2015 the Scientific Working Group on DNA Analysis Methods published the SWGDAM Guidelines for the Validation of Probabilistic Genotyping Systems . STRmix™ is probabilistic genotyping software that employs a continuous model of DNA profile interpretation. This paper describes the developmental validation activities of STRmix™ following the SWGDAM guidelines. It addresses the underlying scientific principles, and the performance of the models with respect to sensitivity, specificity and precision and results of interpretation of casework type samples. This work demonstrates that STRmix™ is suitable for its intended use for the interpretation of single source and mixed DNA profiles.