We are writing in response to a recent letter appearing in Forensic Science International: Genetics entitled “Commentary on: Bright et al. (2018) internal validation of STRmix™ – A multi laboratory response to PCAST, Forensic Science International: Genetics, 34: 11–24″, authored by Dennis McNevin, Kirsty Wright, Janet Chaseling, and Mark Barash [1] (hereafter MWCB). In their letter they acknowledge that Bright et al. [2] is a “valuable first step in establishing a foundational validity for mixture interpretation using probabilistic software, as recommended by the PCAST report” and suggest further experiments to “better address this issue”.