Equus caballus semen used as a carrier to increase human DNA from simulated sexual assault swabs for forensic science applications

Abstract

Currently, there are approximately 200,000 untested sexual assault examination kits in the United States. One reason there are so many untested kits is due to the misconceptions associated with DNA analysis. Since its creation, the Sexual Assault Kit Initiative has reported that 97,000 kits have been tested to completion. While grants are helpful for decreasing the backlog, there are instances where funding has run out or been cut, allowing for a resurgence in the backlog. Therefore, research and development are necessary to reduce the sexual assault examination kit backlog. Conventional differential extraction remains the primary method for separating sperm and epithelial cells despite causing a 94%-98% loss of sperm cells. Despite nearly forty years of innovations, there are no methodologies that improve the yield of male DNA without sperm cell loss. Recent advancements in technology involving carrier RNA have been used to dramatically increase the male DNA recovery without sacrificing sperm cell yield. Therefore, this research investigated the use of a non-human semen sample (horse) as a carrier method to determine if a non-human carrier DNA could be used in place of RNA. It was hypothesized that the carrier DNA should act as a protective barrier during the washing steps of differential extractions reducing sperm cell loss. The thesis studied simulated sexual assault samples in triplicate. The samples were extracted using differential and organic extractions. Finally, the DNA was quantified using Quantifiler™ HP kit to determine the overall human DNA yield. Despite the addition of non-human semen, the DNA concentrations of the experimental group were lower than the control. Therefore, the hypothesis was refuted due to decreased human DNA with the samples containing horse semen. Future research should focus on creating a more tightly packed sperm cell pellet during the centrifugation process.