Abstract
This thesis investigates the use of X-ray Computed Tomography (XCT) when identifying toolmarks on the inner barrel surface of modified/converted firearms. This was done by replicating documented examples of converted firearms on similar barrel material and then using XCT to produce 3D scans of the surfaces. The resulting data then analysed using Areal Cross Correlation (ACCFMAX). In the UK firearm ownership is bound by strict regulations which in turn makes it hard for individuals to illegally obtain them. Due to this, individuals turn to the acquisition of illegal firearms such as modified/converted firearms. Converted firearms can cover those which are legal to own such as blank firing guns. Once purchased these firearms are converted with minimal engineering knowledge, such as drilling out the barrel, and rendered criminally active. The physical modifications leave a ‘fingerprint’ of toolmarks on the inner barrel geometry and surface which are consequently imprinted, or new marks created by material removal mechanisms, onto any ammunition discharged from that firearm. Current methods of toolmark examination rely on the comparison of recovered crime scene bullets and cartridge cases and test fires of suspected firearms. Although implemented into current forensic practises these methods have limitations and have seen unreliable for modified/converted firearms. By measuring the inner barrel surface directly,it can offer forensic examiners additional, previously deemed inaccessible, surfaces in which toolmark comparison can be undertaken. In terms of modified/converted firearms these toolmarks can be individual to a specific source. The results showed that XCT provided a novel solution for the recovery of information regarding barrel modification at larger spatial scales. At present, the resolution of standard industrial XCT systems may not be sufficient to resolve the finest toolmarks on the inner barrel surface and further investigation would be needed for the compatibility with ACCFMAX. However, this does not preclude the use of XCT in future when standard systems routinely operate at smaller spatial scales. Barrel casting, although a cheaper method, was not considered due to the aim being whether XCT can provide the necessary information about the firearm modifications without the need to remove the evidence from the packaging. Therefore, preserving the continuity of the evidence and any forensic trace evidence which has not been recovered.
| Date of Award | 29 Apr 2025 |
|---|---|
| Original language | English |
| Supervisor | Liam Blunt (Main Supervisor), Paul Bills (Co-Supervisor) & Katie Addinall (Co-Supervisor) |