Like prosecuting attorneys, forensic scientists have a much different role in solving a crime than what a law enforcement officer would have. Crime lab personnel must work with prosecuting attorneys, defense attorneys and the investigating officers, so they must maintain a high level of objectivity and work to stay away from being biased toward one side or the other. In processing evidence and making sure that the validated procedures are followed, however, they are meticulous in their work and very biased toward correct processing. This is particularly so in DNA evidence processing because so much is spent on the technology, equipment, materials and training. DNA processing is expensive, so getting it right is imperative.
To ensure the best quantity and quality of sample is processed, DNA techs will spend a considerable amount of time working with the investigators so they fully understand where the DNA material has been deposited and where they should collect from. In the serology step, crime lab personnel know there is a finite amount of DNA material, so there are only so many chances to obtain the DNA needed to produce a viable profile. However, despite diligently working to get the best sample possible, there are many times where the collection tool is not conducive to the evidence surface and where the DNA material may be deposited.
For example, if there is suspected touch DNA on a victim's shirt, the serologist may choose from the cutting, scraping, swabbing or taping methods - all of which are effective to the degree it can access the DNA material at the top of the surface. If the limited DNA material is embedded in the fibers, or spread over a relatively large area, however, none of these collection methods may be effective.
This type of a scenario is the ideal candidate for the M-Vac collection method as the spray-vacuum combination can penetrate deeper into the fibers and apply sufficient force to pull the DNA material out of the shirt. Studies and real world experience have shown that the M-Vac collects 5-10X more than the traditional collection methods in touch DNA cases like the one described here, so utilizing the robust collection of an M-Vac, even after another method failed, can often times collect sufficient DNA material to generate a viable DNA profile. Forensic scientists that have access and utilize an M-Vac System have shown they can produce DNA profiles from cases that may otherwise never get solved.