Police forces have encountered privately made firearms since the last century, making them no longer an unusual sight. Initially, these firearms were rudimentary and improvised, such as zip guns. However, advancements in manufacturing methods and technologies have led to more reliable and robust models. A significant evolution occurred around the 2010s with the advent of commercially available 3D printers. The 2013 release of the 3D-printed Liberator marked the beginning of international attention to this topic, which has periodically re-emerged and been officially recognised as an emerging issue by several law enforcement agencies in the 2020s. This technological advancement not only enhanced manufacturing methods but also fostered a highly connected and active community. Over the past decade, 3D-printed firearms have evolved significantly and can now be compared to conventional firearms in terms of reliability and functionality.
Although the issue of 3D-printed firearms has been recognised, scientific research in the field of forensic sciences was slow to emerge, creating a gap between forensic knowledge and the actual state of affairs. Nevertheless, these initial research projects laid a critical foundation for further studies. This doctoral thesis aims to bridge this gap by building on the existing knowledge. The research focuses on two primary areas: Intelligence and forensic investigation. The intelligence component aims to describe and quantify the phenomenon of 3D-printed firearms, examining their development as well as their prevalence in real life cases. The investigation component seeks answers about the source of these firearms, which can be uncovered through a detailed examination of 3D-printed objects and firearms.
The intelligence projects tracked the evolution and prevalence of 3D-printed firearm designs in police cases, revealing a significant rise since 2020. Despite their increasing presence, these firearms remain a marginal issue compared to other concerns. Notable regional differences include the dominance of hybrid models in Europe and PKCs (Parts Kit Completions) in North America due to varying laws. The projects underscore the shift from F3DP (Fully 3D-printed) to more reliable hybrid and PKC designs, highlighting the growing importance of this issue and the need for heightened attention.
The investigative component involved firing tests of various F3DP and hybrid firearms, confirming their functionality while noting reliability issues in some cases. Notably, hybrid designs demonstrated improved performance and reliability. For the subsequent forensic examination of the traces produced by the firing, a novel approach based on forensic profiling and coupled with a multi-criteria method was implemented. This approach enabled the creation of profiles for the analysed traces, which are designed to contain information on the manufacturing conditions. Initially serving as investigative leads, these profiles help define and narrow down the 3D printing infrastructure used in firearm production. Subsequently, these same profiles were employed for comparison purposes, successfully associating traces with a selected set of 3D printing infrastructure (software and hardware).
This research has provided foundational knowledge for future projects, emphasising the importance of a multi-disciplinary approach to effectively address the challenges posed by 3D-printed firearms. It also underscores the need for collaboration across various forensic disciplines, including digital forensics, analytical chemistry, and firearms and tool marks examination. Continued advancements in understanding and addressing 3D-printed firearms will be crucial for law enforcement and forensic science communities moving forward.