An Investigation of Touch DNA Collection Methods from Clothing: Traditional Cutting Techniques Versus a Wet Vacuum System
by Wander, Marc John, M.S., UNIVERSITY OF CALIFORNIA, DAVIS, 2014, 52 pages; 1565737
This study explored an innovative method for recovering a male offender’s touch DNA deposited on the external side of a cotton t-shirt worn by a female. Traditional cutting procedures were compared, in parallel, to a novel wet vacuum system, called the M-Vac®. This investigation compared these two collection methods to discover which method resulted in a higher yield of DNA, and also examined the relative amounts of male and female DNA obtained from clothing worn by a female and grabbed by a male, with the intent of mimicking an assault. The collected DNA was extracted and then quantified using the Quantifiler® Duo DNA Quantification Kit. STR profiles were analyzed using the AmpFISTR® Identifiler ® PCR Amplification Kit. The average yield of male DNA obtained after a male grabbed the shirt with dry hands was 1.5 ng and 14 ng for cuttings and M-Vac samples, respectively. Compared to cuttings, this demonstrated a 9.7 fold increase (p = 0.0079) of male DNA when the M-Vac was employed for collection. Another variable explored was the impact sweat may have on the amount of touch DNA deposited. The average yield of male DNA obtained after a male grabbed the shirt with sweaty hands was 4.5 ng and 25 ng for cuttings and M-Vac samples, respectively. Compared to cuttings, a 5.8 fold increase (p = 0.0042) of male DNA was observed when the M-Vac was used for sample collection. In this study, the M-Vac was significantly more effective at obtaining touch DNA than fabric cuttings, thus warranting further investigation. The M-Vac could be useful for recovering touch DNA as evidence in the forensic science field.