Recommendations for Selection Areas for the Collection of Sexual Assault Evidence from the Oral Cavity

In this study, female to male oral sex occurred between seven participating couples to determine an efficient collection method for male cellular material located in the oral cavity. One cotton and one nylon swab were simultaneously used to swab two areas of the oral cavity at one, six, twelve, and twenty-four hours post-fellatio respectively. These areas included the lips (utilizing moist and dry swabs) and the inside of the mouth with volunteers receiving specific instructions on how to swab. YSTR profiling was performed on each swab with the subsequent profiles compared to the reference profile of the male. Full YSTR profiles (defined as profiles with at least 22 of 23 alleles matching the male) were obtained in 81% of swabs collected at the one-hour time interval, 67% of swabs at the six-hour time interval, 62% of swabs at the twelve-hour time interval, and 53% of swabs at the twenty four-hour time interval. A higher percentage of full profiles were obtained with lip swabs. No observable difference in the ability to obtain YSTR profiles was found between the use of cotton and nylon swabs. The study yielded DNA success rates typically higher than other similar published studies which typically rely on laboratory data from sexual assault evidence. Recommendations from the study include swabbing both the lips and inside of the mouth of victims of oral sexual assault in a manner described in the study at a time frame up to at least 24 hours post-incident.