Optimization of touch DNA collection from fired cartridge casings using the M-VAC cell collection system
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Citation
Abstract
Brass and nickel-plated fired cartridge casings (FCCs) are among the most common type of evidence encountered by crime agencies and are commonly collected for touch DNA. While the collection of touch DNA on both of these FCCs has been shown to have low success rates, brass FCCs appear to pose more difficulties due to the presence of copper ions that are known to have degradative and inhibitory effects on downstream DNA analysis.The microbial vacuum (M-VAC®) cell collection system is a sterile wet vacuum device that uses buffer to agitate a sample in order to more effectively loosen the cells that were deposited on the surface of an item. A new method known as the Bardole methodTM, which utilizes the vacuum filtration feature of the M-VAC®, has been proposed as a collection method for touch DNA on FCCs.
The purpose of this research is to optimize method collection of touch DNA from FCCs using the M-VAC®. Four methods, including the Bardole methodTM, that incorporate the use of the vacuum filtration are compared to assess the relative successes in collecting touch DNA from brass and nickel-plated FCCs. Chelating-agents that to bind copper ions and reduce the degradative and inhibitory effects on DNA analysis were also assessed. The three remaining methods incorporate one of the following chelating agents each: Chelex® Beads, Glycine-Glycine-Histidine (GGH) protein, and Ethylenediaminetetracetic acid (EDTA).
Results indicated that neither the EDTA nor Chelex® methods were effective in collecting touch DNA from nickel-plated and brass FCCs. Both the Bardole methodTM and GGH method demonstrated comparable results when being used to collect saliva from FCCs and touch DNA from fired and unfired cartridge casings. One touch DNA sample collected by the Bardole methodTM rendered a full and complete profile from one nickel-plated FCC. A further modification of the GGH method demonstrated increased success and resulted in the generation of one extensive partial profile for nickel-plated FCCs.
The Bardole methodTM yielded the best overall results when performing DNA collection of touch DNA on FCCs. However, comparisons of DNA concentrations, degradation and the relative DNA recovery efficiency values indicated that the GGH method demonstrated more potential to successfully collect touch DNA from brass FCCs. Thus, further research is required to determine whether the incorporation of a chelating agent, namely the GGH protein, should be incorporated into the collection method for FCCs to maximize success.
Description
2024