P0236 - Utility of physical evidence collected in child sexual assault cases

Background: Sexual assault of children is both a medical and a criminal problem. Healthcare providers are commonly used to collect evidence. Limited data are available regarding case outcomes related to evidence collection in pediatric sexual assaults.

Objective: To determine which types of physical evidence collected in sexual assault kits are associated with the arrest of a perpetrator.
Design/

Methods: This retrospective cohort study evaluated results of evidence analyzed from the sexual assault kits of children in Kentucky ages 0-17 by the Kentucky State Police (KSP) from November 2000 to April 2015. Specimens were organized by what yielded the positive result (blood, semen, saliva) and from where the specimen was obtained (clothing, body part). These kit data were compared to KSP records of sexual assault arrests occurring between July 2007 through January 2018. Descriptive statistics were determined, and chi-squared statistics and logistic regression were used to assess for correspondence of positive assault kit specimen with arrest.

Results: 437 paired cases of arrests and corresponding assault kit data were available for analysis. Median age was 15. The median time from assault to forensic exam completion (when known) was 16 hours. In total, 52.4% of cases yielded at least one positive result. Breakdown of the specimen types and locations is in the table. Notably, vaginal/penile (19.2%) and underwear (17.2%) swabs yielded DNA for sequencing far more frequently than other sites. Univariate analysis did not reveal any particular result that was more likely to yield an arrest. Logistic regression analyzing the 307 cases with complete data showed an OR of arrest of 2.186 (95% CI 1.188 – 4.024) for presence of foreign DNA in the victim’s underwear when compared to no foreign DNA present.
Conclusion(s): Swabs of areas other than vaginal/penile and underwear infrequently yield adequate DNA for sequencing. Only DNA found in underwear is associated with the arrest of a perpetrator.