Semen extraction efficiency and recovery before and after washing from reusable period underwear

When sexual assault evidence kits do not yield biological evidence demonstrating sexual contact, clothing such as undergarments is evaluated for the presence of semen. Menstrual underwear is a new type of undergarment and feminine product encountered as evidence in sexual assaults. They are composed of absorbent and leak-proof layers and can be washed and re-worn multiple times. The objective of this work was to determine a best practice for semen and DNA recovery from reusable menstrual underwear. Simulated postcoital samples were deposited on three different brands of menstrual underwear, and alternate light source evaluation failed for two of the three brands tested, though acid phosphatase testing was positive for all three brands tested. Testing of individual layers versus cuttings of a portion of the stain found that a full-depth cutting results in optimal biological sample recovery. Mock postcoital deposits were then washed once or twice and subjected to serological and DNA workflows, with varying results in acid phosphatase and P30 testing after washing once or twice between brands. However, sperm recovery was successful in all samples, and complete short tandem repeat (STR) profiles were obtained from both sperm and nonsperm fractions from all samples, regardless of washing status. With these findings, while sperm recovery has the highest likelihood of success with a full-thickness cutting, forensic scientists should be cautious in depending on ALS for stain location. Additionally, biological materials remain in these brands of menstrual underwear after washing, and therefore, biological material from previous sexual contact could remain and be detectable.