Touch DNA constitutes the majority of biological traces analyzed in forensic casework. Their recovery and subsequent laboratory processing remain challenging due to their invisible nature and frequently low quantity and quality of DNA. Conventional recovery techniques such as swabbing or adhesive tape lifting may present limitations, such as reduced recovery efficiency, an increased risk of contamination, and restricted applicability on large surfaces or in hard-to-reach areas. To address these challenges, the DNA-Buster was developed, a dry vacuum-based collection system that has previously been reported to show superior performance compared with swabbing on textile substrates. However, evaluation by the intended end users, namely forensic crime scene investigators, has so far been lacking.

The aim of the study was therefore to assess the applicability of the DNA-Buster in routine police work. Contact traces were collected by crime scene investigators from worn T shirts using the DNA-Buster. In addition, user feedback regarding the safety and intuitiveness of handling was obtained to identify potential needs for further optimization. A simulated offender victim scenario was implemented to evaluate the performance of the DNA-Buster under realistic conditions in comparison with standard recovery methods, with particular emphasis on the detection and interpretation of DNA mixtures. Furthermore, the individual shedding status of the investigators was assessed, as they acted both as DNA donors and as trace collectors, to increase awareness of potential contamination risks when securing evidence, particularly among strong shedders.

The results confirmed that the DNA-Buster was successfully operated by the participants and yielded consistent DNA quantities independent of collection duration. Quantification and genotyping results confirm improved performance on textile substrates compared with swabbing and results comparable to adhesive tape lifting. In addition, the DNA-Buster offers advantages over adhesive tape methods with respect to handling with reduced contamination risk and more efficient downstream laboratory processing.

The observed intra and inter individual variability in shedding of the participants further highlights the inherent challenges associated with touch DNA. Regarding a substrate specific recovery, our results indicate that swabbing should be avoided for textiles, whereas tape lifting or vacuuming should be preferred. Based on these results, the DNA-Buster is currently implemented as a stationary device for the recovery of traces from textile evidence at the Police Basel Landschaft. Current limitations of the dry vacuuming approach include its evaluation primarily on textile substrates, while the evaluation of its mobile application under operational crime scene conditions is subject of further investigations.

Authors

• Iris Schulz (University of Basel, Department of Biomedical Engineering, Institute of Forensic Medicine, Switzerland)
• Elisa Sohrmann (University of Basel, Department of Biomedical Engineering, Institute of Forensic Medicine, Switzerland)
• Janine Schulte (University of Basel, Department of Biomedical Engineering, Institute of Forensic Medicine, Switzerland)
• Sarah Kron (University of Basel, Department of Biomedical Engineering, Institute of Forensic Medicine, Switzerland)
• Alexander Schocker (Police Basel-Landschaft, Forensic Sciences, Switzerland)
• Oliver Eidam (OTR-Performance GmbH, Switzerland)