Validation of the M-Vac cell collection system for forensic purposes

Abstract

There is need for further development of cellular collection techniques in the field of forensic science. Currently, forensic analysts are limited to the use of swabs, taping, cutting, and scraping methods to collect cellular material. Each of these methods has its own benefits and drawbacks, however, none of them result in 100% recovery of the cells.

The Microbial Vacuum system (M-Vac®), developed by MSI, is a liquid based cellular collection system that was originally developed to collect microbes in the food-processing industry from various surfaces. This research represents a detailed study into the feasibility of utilizing the M-Vac® system for forensic purposes. Specifically, the phosphate buffer used with the M-Vac® was tested to confirm that it does not have a detrimental effect on cellular retrieval. Further, the ability of the M-Vac® to collect cellular material from a variety of substrates was tested. It was determined the M-Vac® can successfully collect both blood and semen from tile, denim, carpet, and brick materials in sufficient quantity for downstream PCR analysis.

Additionally, examination into whether DNA was dispersed during collection due to the significant force of impact of the liquid striking the surface was conducted. Specifically, areas surrounding the sample collection region were swabbed after collection with the M-Vac® and tested. Quantitative PCR analysis showed that DNA was retrieved up to 4 inches away from the collection area. This indicates that the M-Vac® system is a viable cell collection technique for forensic purposes, but only for samples which are isolated (i.e. where there is not another probative sample adjacent to it). If there are two probative samples within the same vicinity, then swabbing or taping is the recommended method of collection.