The Effects of Water Type, Exposure Time, and Water Agitation Level on the Ability to Detect Semen, Sperm, and Human DNA on Cotton Fabric

This study examines the effects of immersion in two types of water, tap water and chlorinated swimming pool water, on semen-stained 100% cotton fabric. The sensitivity of the acid phosphatase (AP) spot test and the ability to extract and quantify DNA in the stain was determined after the fabric was submerged in each water type. In order to determine whether agitation of the water also had an effect on the AP spot test and DNA quantitation, agitation trials were tested against still trials for each water type. The experiment took place over the course of seven days for each trial. The AP spot test was negative as of day three in the agitated tap water trial and both the still and agitated swimming pool water trials, but remained positive until day five in the still tap water trial. The minimum amount of DNA necessary for STR profiling, however, was obtained through day seven for both tap water trials and the still swimming pool water trial. The minimum amount of usable DNA was only obtained through day three of the agitated swimming pool trial. Therefore, DNA quantitation may still be possible and a minimum amount of usable DNA may still be obtained even when the AP spot test is negative for the presence of acid phosphatase. The loss of DNA over the entire seven days of soaking created four regression equations (one for each trial) that can be used to determine the approximate amount of DNA present within a sample if the soaking time is known, or to help determine the approximate length of time semen-stained cotton fabric has been soaking if the quantity of DNA is known.