Immunohistochemical staining of human sperm cells in smears from sexual assault cases

In the routine clinical examination of sexual assault victims, apart from documenting physical evidence of abuse, securing evidence, typically DNA from blood, semen, or saliva, is an important part of the process. Often the presence of semen is considered a most interesting piece of evidence. Not only does it often contain enough DNA for DNA profiling, but it also strongly indicates that an actual sexual act has taken place. The examination of smear slides obtained in sexual assault cases is a time-consuming task especially for the less trained and in cases where the smear only contains few sperm cells. In this work the goal was to develop a procedure to rapidly visualize human sperm cells in smear slides with the use of bright-field microscopy. Using SPERM HY-LITER™ by Independent Forensics, human sperm cells are visualized using a fluorescently labeled mouse antibody which significantly decreases the time used to screen smears. By further using an EnVision+ (DAKO) protocol, it was possible to create an immunohistochemical staining method to visualize sperm cells in bright-field microscopy with the same level of certainty as when using SPERM HY-LITER™.