A systematic evaluation of the DNA collection methods, from different swab types and moistening agents to tape-lifting and direct extraction, revealed that every factor influences the recovery of DNA to a certain degree. There was no single best swab type or moistening agent for all substrates. Rather, different combinations were more suitable for different substrates. EO cotton swab, with its low cost and versatility, could be used to consistently recover trace DNA from casework IED evidence. Solar tape and direct extraction without soaking also recovered more DNA than Officeworks tape and direct extraction with soaking, respectively. The results of this study significantly improved the DNA profiles obtained from IED evidence. The findings from both parts of this study emphasize the need to re-evaluate standard operating protocols, even at the most basic level like DNA collection, with knowledge gained from empirical studies.