Abstract: With sexual assault evidence, the visualization of spermatozoa confirms that ejaculation has occurred. However, microscopic examination of spermatozoa is a laborious process and can sometimes result in sperm cells being overlooked. Here, we present the developmental validation of the SPERM HY-LITER™ kit, which contains a human sperm–specific mouse monoclonal antibody coupled to a fluorescent Alexa 488 dye. The kit was tested using samples of human semen, saliva, blood, and urine, various animal semen extracts, sexual lubricants, and a commercially available spermicidal film. Postcoital vaginal swabs, degraded semen samples, and samples prepared with sample fixation techniques that deviated from the kit-provided protocol were also tested. In each case, the SPERM HY-LITER™ kit was demonstrated to bind only to human sperm cell heads. Limitations to this fluorescent staining procedure include nonspecific staining and increased background fluorescence with extreme heat fixation in some samples.