Statute of Limitations Effect on Forensic DNA Testing Outcomes for Biological Evidence from Sexual Assault Kits: Results from the Detroit Sexual Assault Kit Action Research Project

• Activity Number: 645
• Type: Contributed
• Date/Time: Thursday, August 13, 2015 : 8:30 AM to 10:20 AM
• Sponsor: Government Statistics Section
• Author(s): Dhruv Sharma* and Steven Pierce and Rebecca Campbell
• Companies: Michigan State University and Michigan State University and Michigan State University
• Keywords: sexual assault kit ; forensic DNA testing ; statute of limitations ; CODIS ; continuation-ratio model

Abstract

Large backlogs of sexual assault kits (SAKs) that were never submitted for forensic testing have been found in several US cities, highlighting a serious national problem for the criminal justice system and the need to provide guidance on how to respond to these backlogs. One debate focuses on the utility of testing SAKs for which the statute of limitations (SOL) has presumably expired due to delayed testing, particularly when resources are scarce. Forensic testing aims to extract offender DNA profiles, enter them into the FBI's Combined DNA Index System (CODIS) database, and link them to DNA from other crimes. This can reveal or confirm offenders' identities and even show whether they are serial rapists. DNA testing can be modeled as a conditional incremental process, with SAKs sequentially reaching the CODIS entry, hit and serial assault stages only if they pass stage-specific criteria. A continuation-ratio model demonstrates that entry, hit, and serial assault rates among presumed SOL expired and unexpired rapes do not differ at any stage of the process, justifying testing all SAKs regardless of SOL status.