Data driven optimization of sexual assault case processing

Abstract

In recent years, several forensic laboratories have noted an increase in the number of sexual assault cases submitted for testing, often leading to longer turnaround times. In that context, forensic laboratories may be interested in reviewing their procedures to increase productivity. Here, we present two different strategies that were put in place in our laboratory. First, we changed the way sexual assault evidence kits (SAEK) are processed by implementing an optimized workflow that prioritizes the internal samples (vaginal, anal, and oral). This new procedure allowed for a drastic decrease in turnaround time, while maintaining a similar investigative power.Secondly, we used data from casework to target cases and samples that were likely to yield biological material from the perpetrator, in an attempt to avoid dedicating time and effort to cases for which there is a very low probability of obtaining foreign DNA evidence. Among other things, we looked at the likelihood of obtaining DNA from the perpetrator when the complainant reported the use of a condom, has showered after the assault or when the complainant has no memory of the assault. Results show that those circumstances do not dramatically decrease the probability of finding DNA from the perpetrator.

Keywords

• Sexual assault evidence kit (SAEK)
• Time since intercourse (TSI)
• Skin swab
• Washing
• DNA profile