DNA typing from stained sperm-positive vaginal smears: four rape cases

Abstract

DNA typing from stained sperm-positive vaginal smears was performed in four cases of sexual assault. In Cases 1 and 2, a 6-month-old and a 6-week-old, Papanicolaou-stained vaginal smear with 99% propanol fixation underwent DNA analysis respectively. In Case 1, the HLA-DQα type of the sperm fraction of the smear was able to be determined following PCR, and the possibility of the suspect being the rapist could not be excluded. In Case 2, the possibility that the suspect was the rapist in the crime was excluded based on the results of DNA typing by means of two different single-locus probes. In the remaining two cases, H-E-stained smears after air drying for 4 or 5 months were the material for DNA analysis, and DNA typing was attempted by PCR-based STR system. In Case 3, there was no genetic information from sperm fraction of the smear due to the small number of spermatozoa on the glass slide. Therefore, it was impossible to determine whether the suspect was the rapist or not. In Case 4, sperm DNA from the smear was amplified and typed, and the suspect could be excluded. These four cases demonstrate that stained vaginal smears containing many spermatozoa can be used for DNA analysis in sexual assault cases.