M-VAC manufactured by M-Vac Systems Inc. USA provides a new tool enabling the improved recovery of DNA from difficult surfaces and materials in both quality and quantity. Bob Milne MCSFS FFS takes a look at the M-VAC System and the results achieved by a number of Police services.
The standard method for recovering DNA from most exhibits is to use sterile DNA free swabs. It should be noted that sterile swabs as used for medical uses may be sterile but not necessarily DNA free. It is important to ensure that swabs are certified and labelled DNA Free. In any event an evidence recovery swab is an absorbent tip on a small stick and once used is stored in a plastic tube. This is fine for the recovery of DNA from body fluids or the removal of cells on non-porous surfaces. What about the microscopic traces of body fluids or cells in crevices, in fabrics below the surface? Here swabs can be ineffective and that is why the M-VAC originally designed to recover bacteria from food plants for analysis was utilised in its present form to enable the more effective recovery of DNA.
A recent study by the Philadelphia Office of Forensic Science, was two-fold. In the first part the M-Vac recovered 180 times more than the swabbing of diluted buccal cells from clean cloth swatches. In the second part of DNA recovery of touch DNA on a variety of substrates the M-Vac recovery was on average 5 times more than swabbing in those scenarios. Both validations however showed a significant increase in performance. The M-Vac enables the systematic search of clothing, rock, cement or other porous surfaces and even large-surface sampling from human skin. Both casework and research has shown traditional methods are not as effective as the M-Vac on these substrates. To give readers an appreciation of the effectiveness of the M-VAC system the cases covered below include a cold case whereby useable DNA was recovered from a rough rock used as a murder weapon 18 years ago.
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