The use of micro-CT in the investigation of a case involving 3D printed firearms.

This paper highlights how micro-CT was used to assist in the investigation of hybrid firearms constructed using a mixture of plastic and metal components, as a complementary technique to the physical examination performed by firearms experts. In recent years, there has been an increase in the complexity and sophistication of 3D printed and hybrid firearm designs. This was also the case in the investigation presented herein, with the firearms seized demonstrating a step change in the threat level they pose through their complexity. Thus, we describe how data produced from micro-CT scans was used to help firearms experts study the viability and mechanics of two hybrid weapons prior to dismantling and test-firing. This process aided experts in determining whether components were 3D printed or manufactured through other means, whilst ensuring that a digital record (digital twin) was retained in case evidence was damaged during testing. Finally, we show how the data was presented visually through animations and as evidence in court. This proved to be imperative when communicating to the judge, jury, and wider investigating teams, the complex multiple components and mechanisms within the firearms.