Detection of spermatozoa following consensual sexual intercourse

INTRODUCTION: In cases of sexual assault, the finding of semen can provide crucial evidence. The presence of spermatozoa serves as proof of a sexual act and may give the identity of the alleged perpetrator through DNA-profiling. In most western countries, there are guidelines for standardized examinations of sexual assault victims. For an objective evaluation of the findings, substantial knowledge of aspects regarding consensual sexual intercourse is crucial. The aim of this study was to examine detection frequencies and genital sampling sites of spermatozoa following consensual sexual intercourse. METHODS: In a prospective setting, 60 women underwent forensic examination following consensual sexual intercourse. Specimens were obtained from the external genitalia, the posterior fornix and the cervical canal, and examined using the Papanicolau stain and standard light microscopy. RESULTS: We found that 88% of possible cases were positive for spermatozoa. The posterior fornix was significantly better than the other sites for detection of spermatozoa and the number of spermatozoa decreased significantly over time. In a large sub-group of women who reported that no intra-vaginal ejaculation had taken place during their latest intercourse, a significant number (14%) had spermatozoa in the vagina. CONCLUSION: Spermatozoa were best recovered from the posterior fornix, but spermatozoa were also present on swabs taken from the external genitalia. Detection of spermatozoa is thus possible in cases where a speculum examination is denied.