The widespread availability of consumer grade 3D printers has led to an increase in 3D printed items encountered in criminal investigations, including components associated with improvised or illicitly manufactured weapons. Despite this trend, current forensic guidance provides limited information on optimal DNA recovery from 3D printed substrates, which differ from conventional plastics in surface structure and material properties. This project, led by West Midlands Police in collaboration with Dstl and funded by the Office of the Police Chief Scientific Advisor, sought to establish best practice recommendations for DNA recovery from commonly used 3D printed materials. The study evaluated DNA recovery performance across three substrate types: polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and UV cured resin. Five sampling approaches were compared: wet and dry cotton swabs with water, wet and dry cotton swabs with buffer, FLOQSwabs® with water, FLOQSwabs® with buffer, and adhesive minitapes. Substrates were handled by two DNA donors and sampled at two intervals, within days and after one month, to assess persistence. DNA was extracted using EZ1 Qiagen protocols, quantified with Quantifiler Trio™, and amplified using the GlobalFiler™ system prior to STR profiling. No significant differences were observed between the two sampling timepoints, allowing results to be combined for analysis. Across substrates, swabbing with buffer, particularly when used with FLOQSwabs®, or minitapes produced the highest percentage of expected alleles, representing the most effective methods evaluated. In contrast, cotton swabs moistened with water consistently yielded the lowest percentage of expected alleles, demonstrating reduced performance regardless of substrate type. This work provides a systematic evaluation of DNA recovery methods for 3D printed materials and offers evidence based guidance for forensic practitioners. As 3D printed items continue to feature in an increasing number of investigations, particularly those involving improvised weaponry, validated sampling strategies are essential to ensure reliable DNA evidence capture. The study establishes best practice recommendations and reinforces the need for continued assessment as new materials and printing technologies emerge. Fingermark visualisation methods were also evaluated as part of this research, and further details on this aspect of the work can be provided upon request. © Crown copyright (2026), Dstl. This material is licensed under the terms of the Open Government Licence except where otherwise stated. To view this licence, visit http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3 or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: psi@nationalarchives.gov.uk

Author

• Sally Stansbie (Defence Science and Technology Laboratories, United Kingdom)