Why M-Vac

UC Davis - Post Shower Research

Objective: Determine if the M-Vac is capable of collecting male saliva from a female’s skin after showering.  Many female victims hesitate to report sexual assault, and, in some instances, shower before making a final decision.  Showering can easily remove saliva from skin and can make collection of salivary DNA difficult.  This project aims to explore the amount of salivary DNA that can be obtained while using the M-Vac compared to traditional swab methods with the location of the saliva being known.

ShowerMethods: Apply male saliva in four locations, right and left, on the neck, upper arm, abdomen and lower thighs of the female “victim.”  Apply the saliva in 50 microliters quantities.  Wait 15 minutes for the saliva to dry.  Go about normal activities for four hours, showers and returns for collections.  Use the M-Vac to collect from the right side locations and the swab to collect from the left side locations.

Extraction/Analysis: Extract the DNA using the QIAmp® DNA Investigator Kit (Qiagen).  DNA quantification was done with Quantifiler Duo® Kit (ABI). DNA amplification was done with AmpFISTER® Identifiler® PCR Kit and YSTR Kit (ABI).

Results:  There was no statistical difference between the quantities collected by the M-Vac and the swab.

Conclusions: In some cases, a sexual assault victim will shower before they seek out a forensic exam.  In addition, the victim does not always remember where the perpetrator has touch them.  The traditional swab technique is limited to a small surface area, but the M-Vac can sample large regions of the body.  In this study, the saliva location was known, potentially giving the swab an over-representation in the results.  When the saliva location is unknown, the M-Vac would be more effective.