Large stockpiles of untested sexual assault kits (SAKs; or “rape kits”) have been found in police departments throughout the United States. SAKs contain biological evidence (semen, saliva, and blood) that can be analyzed for DNA to inform investigations and prosecutions. However, when SAKs are not tested, it is less likely offenders will be held accountable and they may commit additional crimes. Given the utility of SAK evidence in protecting public safety, a growing number of states are passing mandatory SAK testing laws. In this study, we tracked a sample of previously unsubmitted SAKs collected in Detroit, MI to explore what crimes might have been prevented, based on mandates in the Michigan Sexual Assault Evidence Submission Act (2014). For our first research question (Did the rate of offending increase from before to after a SAK could have been tested?), the analyses revealed significant escalation in criminal activity over time. These offenders committed five additional crimes (on average) after their earliest-known SAK could have been tested (range 0–49 crimes), including other sexual assaults, physical assaults, and homicides. For our second research question (Are multiple crimes committed by a subset of repeat offenders?), the results indicated most of this criminal activity was linked to a subset of prolific offenders. For our third research question (How many of these criminal incidents could have been feasibly prevented by timely testing?), the analyses documented that up to 320 additional sexual assaults, plus over a thousand other violent crimes, might have been prevented with timely SAK testing. (PsycInfo Database Record (c) 2022 APA, all rights reserved)