You are a forensic scientist. For today, your supervisor tells you to perform a confirmatory test for semen on Item D. You recover Item D from the evidence locker. Item D is a vaginal swab from a sexual assault kit. An AP Spot Test has already been performed on the swab, with a positive result. You cut off a small portion of the swab. You agitate the swab in a small tube with water. You smear this water onto a microscope slide and stain the slide with red dye and green dye. You look for sperm cells under a microscope, but do not observe any sperm cells. Explain.
