Application of hematoxylin reagent for sperm cell separation in sexual crime evidence

Seminal evidence obtained from a sexual crime scene provides clues for solving a case through forensic analysis. However, most evidence collected from sexual crime scenes is a mixture of sperm cells and vaginal discharge. Therefore, separating the sperm cells from the seminal evidence is very important. In this study, we developed a separation method for effectively separating sperm cells using differential extraction with commercially available sperm staining reagents such as hematoxylin and nigrosin. Hematoxylin (0.03 % v/v) effectively stained the sperm cells in ATL and TNE lysis buffer, while nigrosin did not. The loss of sperm cells during washing of the specimen was minimized using the differential extraction method. Subsequently, genomic DNA was extracted from the hematoxylin-stained sperm cells and subjected to short tandem repeat genotyping. We observed no interference from hematoxylin. These results indicate that hematoxylin can be used to stain sperm cells and thus facilitate subsequent genetic identification.