Cartridge casings made from transition metals can be examined ballistically and also serve as significant evidence by containing touch DNA. However, the success rate of profiles obtained from this type of evidence is generally low. To enhance the success of DNA profiling from suspects' biological evidence, using swabs moistened with chemicals can be beneficial. Swabs are typically moistened with water, whose hypotonic nature disrupts cell integrity, causing the release of DNA. However, water is not the only agent used for moistening swabs; various buffer solutions are also utilized. The ability of swabs to transfer touch DNA depends on the type of buffer solution used. Sodium dodecyl sulfate (SDS), a strong anionic detergent, denatures non-covalently linked secondary and tertiary structures to increase the release of bound DNA. Another buffer solution used for swab moistening is Te+4 buffer, which contains EDTA and Tris. EDTA chelates metal ions, inactivating enzymes that could potentially damage DNA, while Tris adjusts the pH to an optimal level. This study aims to compare the effectiveness of microfibre and cotton swabs moistened with SDS, Te+4 buffer, and water in recovering genetic material from blood and epithelial cells deposited on brass cartridge casings. The study also evaluates the impact of firing on the quality of DNA profiles. Among the profiles obtained, the swabs moistened with SDS produced the highest rate of complete profiles at 44%, while the lowest rate of complete profiles at 22% was observed with swabs moistened with Te+4 buffer. SDS is particularly advantageous over water when used on casings with epithelial cells. Microfibre swabs are more effective in eliminating degradative factors caused by firing, thus enhancing profiling success. Comparisons of the RFU values indicate that casings yield lower values compared to cartridges, supporting the negative impact of the high heat, pressure, and residues generated during firearm discharge.
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