Investigating Touch DNA Success Rates in Vehicle Sites for Hit-and-Run Casework

This study evaluated the effectiveness of Touch DNA recovery from four key vehicle contact points—steering wheel (SW), gear shift (GS), interior door handle (IDH), and exterior door handle (EDH)—in the context of hit-and-run forensic casework. 1769 samples were collected from 359 vehicles processed between 2020 and 2023. Statistically significant differences were observed in the quantity and quality of DNA recovered across these sites (p < 0.05). The steering wheel yielded the highest DNA success rates, followed by the gear shift, whereas the exterior and interior door handles demonstrated substantially lower recovery efficiency. These findings underscore the critical role of strategic sampling site selection in maximizing evidentiary outcomes. The results support prioritizing the steering wheel and gear shift as primary targets for DNA collection in vehicle-based investigations. The study highlights the practical utility of Touch DNA in linking individuals to vehicular crimes and calls for further research into alternative sampling techniques and contamination control measures to optimize forensic DNA recovery protocols in real-world hit-and-run scenarios.