Influence of physiological activation on Touch DNA deposition and STR profile quality during competitive computer...

Touch DNA recovery from handled objects is influenced by donor, substrate, transfer, persistence, and collection-related factors; however, the role of short-term physiological activation during contact remains poorly understood. This pilot crossover study evaluated whether competitive gaming was associated with differences in Touch DNA deposition and STR profile quality on computer input devices compared with routine computer browsing. Twenty-four adult participants completed both 30-min activity conditions in randomized order, separated by a 30-min washout period. Heart rate and palmar moisture were measured before and after each activity, and Touch DNA was collected from predefined keyboard and mouse regions, generating 96 experimental samples. Samples were processed using a standardized forensic DNA workflow comprising extraction, quantification, GlobalFiler™ STR amplification, capillary electrophoresis, and profile assessment. Baseline physiological measures were comparable between conditions. Competitive gaming elicited significantly greater physiological activation than browsing, including higher post-activity heart rate (89.6 ± 10.7 bpm vs. 75.8 ± 8.4 bpm; p < 0.001) and palmar moisture scores (48.9 ± 7.4 vs. 36.2 ± 5.6; p < 0.001). Gaming was also associated with significantly greater recovered DNA quantity (p < 0.001, Cohen's d = 1.64) and detected autosomal alleles (p < 0.001, Cohen's d = 1.37) than browsing. STR profile quality was similarly improved, with higher profile completeness (p < 0.001, Cohen's d = 2.12) and mean profile RFU (p < 0.001, Cohen's d = 2.46) following gaming. At the participant-condition level, changes in palmar moisture showed strong positive associations with mean DNA recovery across devices (r = 0.89, p < 0.001), device-averaged profile completeness (r = 0.83, p < 0.001), and device-averaged mean RFU (r = 0.90, p < 0.001), whereas change in heart rate showed a more moderate association with mean DNA recovery (r = 0.49, p < 0.001). These findings indicate that activity-associated physiological and behavioural conditions, particularly local hand-surface moisture, may contribute to variation in Touch DNA deposition and STR profile quality on high-contact computer devices. However, the independent contributions of physiological activation and intensified manual interaction could not be separated. The results support a more contextual approach to Touch DNA interpretation in which activity intensity and local hand-surface conditions are considered alongside donor variability, substrate characteristics, transfer mechanisms, and case circumstances. This study provides preliminary evidence that the physiological and behavioural conditions accompanying an activity may represent underappreciated contributors to Touch DNA variability and activity-level interpretation.