Police field trial and exploratory laboratory optimization of the DNA-Buster

DNA analysis is a powerful tool in crime scene investigations and has become increasingly sensitive in recent years. This is particularly relevant when dealing with touch DNA, a challenging type of evidence due to its invisible nature, and often limited quantity and quality. Conventional collection methods such as swabbing or taping can have certain limitations, including low recovery efficiency, handling with increased risk of contamination, and difficulties in sampling large surfaces or accessing small niches and corners. To address these challenges, the DNA-Buster was developed, a dry-vacuum DNA collection device that has demonstrated superior performance on textile substrates in previous research. However, the device has not yet been tested by its intended end users. Thus, this study aimed to evaluate the feasibility of implementing the DNA-Buster within police forces using touch DNA samples from worn T-shirts collected by the crime scene investigators themselves. The study sought to gain user feedback regarding the device's secure and intuitive handling and to identify areas for optimization, such as a 3D-printed pipette tip prototype for sampling. A mock aggressor-victim scenario was additionally investigated to examine how the DNA-Buster performs on textiles compared to standard collection methods. Lastly, for the first time, the individual shedder tendencies of the crime scene investigators acting both as donors and collectors were assessed, aiming to increase the awareness of the contamination potential when handling evidence. The study outcomes confirm that the DNA-Buster outperforms swabbing on textiles and shows comparable results to taping regarding DNA concentrations and profiling success of touch DNA. These findings highlight the importance of selecting most suitable methods for each substrate to obtain optimal results. This is particularly relevant as some police forces, for various reasons, still rely on swabbing for textiles, despite its lower profiling success. Next, the DNA-Buster was operated efficiently by all collectors after minimal training and generated consistent DNA concentrations independent of collection time. Compared to taping, its advantages lie in more practical application with respect to evidence handling by police investigators and easier laboratory processing. With respect to the shedding test, observed intra- and interindividual variability among donors underscore the challenges associated with touch DNA experiments. Following this successful trial in collaboration with the intended end users, the DNA-Buster is now suitable, as a stationary tool, for the collection of trace DNA from textile evidence. However, its mobile use at crime scenes requires further evaluation based on future feedback from crime scene investigators.