Rapid stain biomarker: A novel tool for forensic detection of semen (effect of time, different fabrics and vaginal secretions on its reliability)

Abstract

Abstract Background The identification of semen stain is one of the most common human stains that can provide crucial information for crime scene reconstruction and forensic investigation. In sexual assault cases semen identification helps to prove victim’s allegations it also provides a material for DNA analysis that generate the genetic profile of the alleged suspect. The rapid Stain Identification of Human Semen (RSIDTM-Semen) bioassay is designed to detect specifically the presence of human semenogelin. Test development is completed within 10 minutes and can detect as little as 2.5 nL of human semen and it does not cross-react with other human or nonhuman tissues. The detection protocol can be completely integrated into the procedures for DNA extraction and analysis. Aim To assess the efficacy of RSIDTM – Semen strip test for the detection of human semen under some different variables (different fabrics, different time intervals and mixed with vaginal secretions) in order to be used in the routine forensic work of sexual assault cases and for further personal identification. Methodology: Semen samples were collected from four male participants. Vaginal specimens were collected from four female participants on cotton, linen or nylon-tipped swabs (2 swabs from each female). Each semen sample was divided into two portions; one used for semen only test group and the other mixed with vaginal secretions for the mixed test group. One of the fabrics tipped vaginal swab was mixed with semen for the mixed test group and the other used as a positive control group to test the sensitivity and specificity of the RSIDTM – Semen strip. The semen samples were deposited over different fabrics at the same time. All the samples were left to dry for 15 minutes at room temperature then extracted and analyzed according to the protocol designed for The Rapid Stain Identification Test (RSIDTM – Semen). The collected samples were studied as two test groups and one control group. Each of the previous groups, was categorized into 4 subgroups (a, b, c and d) according to the time interval of semen extraction (zero (on the spot), 2, 4, 6 and 10 days respectively). Results Semen could be identified in 100% of tested samples of the semen only group as well as of the combined semen and vagina group over cotton and linen fabrics at all the different tested time intervals. However, semen extracted from nylon fabric was identified in tested samples of the semen only group and of the combined semen and vagina group only at zero time only and couldn’t be identified at the rest of tested time intervals. Conclusion the current study evidenced that the new RSIDTM-semen kit is a reliable method for semen identification over different types of fabrics even in the presence of vaginal secretions. It also resists environmental factors up to 10 days.