Urine specimen collection following consensual intercourse - A forensic evidence collection method for Y-DNA and spermatozoa

The purpose of the prospective research was to evaluate the benefit of urine specimen as a collection technique for biological forensic evidence in adult volunteers following consensual intercourse. For detecting Y-chromosomal material Buccal Swab Spin Protocol(®) was used in DNA extraction and purification and samples were analysed with Quantifiler Y Human Male DNA Quantification Kit(®). The time frame for positive Y-DNA was evaluated. Immediate microscopy for detection of spermatozoa was performed. Y-DNA was detected in 173/205 (84.4%) urine samples. Of the 86 first post-coital void urine samples available, Y-DNA was detected in 83 (96.5%) specimens. Of the 119 urine samples from volunteers with post-coital activities Y-DNA was still measurable in 70 (58.8%) urine specimens. The male DNA amount was below 0.023 ng/μl in 28/153 (18.3%) urine samples. Of the 22 urine samples obtained after 24 post-coital hours, 9 (40.9%) were still Y-DNA positive. No associations were found between coital durance, coital frequency during the past two weeks prior to the study intercourse, post-coital activities, and the urine sample Y-DNA positivity. Of the 111 urine samples where the immediate microscopy was performed, in 66 (59.5%) samples spermatozoa were verified and one sample even contained motile spermatozoa. Microscopy detected 66 (67.3%) and failed to detect spermatozoa in 32 (32.7%) of Y-DNA positive samples. In addition to conventional invasive swab techniques, urine samples seem to be an effective biological trace collection method for Y-DNA and spermatozoa within 24 h following penile-vaginal penetration. Furthermore, it may be considered as a non-invasive collection method in suspected acute child sexual abuse cases to diminish time delay in forensic evidence collection and to improve patients' positive attitudes towards evidence collection.