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Methods for semen detection can be used as forensic tools to determine a crime or in the home to detect an unfaithful spouse. The most popular methods for detecting semen are the use of chemicals to determine the presence of prostate specific antigens (PSA), acid phosphate (AP) or microscopic examination. Non-chemical examinations can be performed using an ultraviolet (UV) black light and careful physical inspection of the exposed area.
The PSA semen detection test can be performed in a forensic lab or at home. This test works by identifying PSA found on a substrate that is suspected of coming into contact with seminal fluid. Seminal fluid could be found on objects such as underwear, bed sheets or articles used for feminine hygiene. Samples of the substrate being tested or scrapings can be used to mix with the chemicals that detect semen. Home tests might reveal results in about 10 minutes, and lab results could take as long as 48 hours.
Semen detection to determine the presence of acid phosphate can also be used at home or in a laboratory setting. This method could be used in much the same way as the PSA test. AP can be found in bodily fluid other than seminal fluid, which might cause this method of testing to be less reliable than the PSA test. Experts often suggest that the AP procedure should be used in conjunction with other testing methods for home and laboratory applications.
Forensic laboratories could also use different microscopic techniques for semen detection. Primarily, the substrate suspected of containing seminal fluid will be removed and washed with chemicals that release any sperm. Slides could be prepared and viewed under a microscope to look for the presence of sperm. These techniques might be used to solidify physical evidence for court proceedings.
Ultraviolet black light can be used as a non-chemical way to determine the presence of semen. Seminal fluid can fluoresce in the proper conditions. When a UV black light is shown on the substrate in question, seminal fluid could appear to be a bright blue color. Specific chemicals that help illuminate the proteins that are found in seminal fluid could also be sprayed on the stain to assist in semen detection.
Careful physical inspection of a substrate could also be a preliminary method used for semen detection. The visual appearance of seminal fluid on items such as bed sheets could show as a stiff, opaque or translucent stain. If the stain is still fresh, a specific odor associated with seminal fluid might still be detectable. The stain might not be seminal fluid, however, so other testing methods should accompany physical inspection to rule out the possibility of an error.