Adhesive tape versus swabbing for touch DNA collection: A direct PCR approach with the VeriFiler Express Kit

This study compares two collection techniques - swabbing and adhesive tape - for obtaining touch DNA samples suitable for direct typing with the VeriFiler® Express Kit. Touch DNA, defined as genetic material deposited on surfaces following human contact, plays an increasingly important role in forensic investigations by enabling the analysis of trace biological evidence for potential suspect identification. Samples were collected from two controlled surfaces: sterile glass and a mobile phone. A total of 100 samples were obtained using both methods and analyzed for DNA quantity and quality, specifically the number of loci successfully amplified, profile completeness, and allele dropout rates. Results demonstrated that adhesive tape was more effective than swabbing in recovering DNA. Complete profiles were obtained from 85 % of adhesive tape samples, whereas 60 % of swab samples yielded only partial profiles (≥20 loci). The swabbing method exhibited higher allele dropout rates (30 %) compared to adhesive tape (15 %). These findings suggest that adhesive tape more efficiently captures cellular material from smooth surfaces and is better suited for direct PCR amplification without DNA extraction. This no-extraction workflow reduces handling time, minimizes contamination risk, and accelerates forensic processing. The findings support incorporating adhesive tape collection as a standard procedure for touch DNA recovery in forensic practice, thereby improving the accuracy and reliability of trace DNA evidence in criminal investigations. Future work by our research team will evaluate performance across a wider range of surfaces and environmental conditions, aiming to further refine collection protocols in laboratory and field settings.