Forensic Forays: Using X-ray Technology to Analyse Modified and Converted Firearms

small arms survey
5 min readAug 16, 2021

By: Hannah Smith, Katie Addinall, and Liam Blunt

Europe and the UK along with it, have some of the strictest laws regarding the possession of firearms. However, this alone does not stop the use of firearms in crime; partly due to the prevalence of modified and converted firearms seen throughout the continent which are being used by criminals, from gang-related street violence to terror attacks.

Modified and converted firearms are extremely popular with criminals as they are easy to obtain and cheap. Due to ease of procurement and the willingness of criminal backstreet ‘workshops’ to carry out modifications, these weapons are a popular choice amongst the criminal community.

Examples of modified and converted firearms could be blank-firing, deactivated, or antique firearms (legal) which are then modified to live-firing weapons (illegal). The modifications may be completed in the country of purchase and then smuggled over international borders or smuggled across and then converted in the destination country.

Although modifications can occur to the whole weapon, the firearm barrel is the typical focus. Here, modifications can range from removing obstructions, enlarging the inner diameter of the barrel to accept modern ammunition, sleeving the barrel, or even replacing the entire barrel completely. Barrel replacements are often dangerous as criminals will use a softer material than the harder metals used by firearms manufacturers. Using a softer material will result in serious damage to the firearm, and ultimately those in the vicinity of it when used.

When modifying the barrels, criminals leave distinctive tool marks on the inner barrel which are important for forensic examiners. Tool marks hold a great deal of information which can be analysed in a forensic setting to not only determine the methods of modification, but also the individual and specific tool used for the modification. An example of this can be seen in Operation Golddust where forensic examiners at NABIS were able to identify a continuing pattern of tool marks on homemade ammunition being collected from crime scenes around the UK. They traced the tool marks back to a single individual — Paul Edmunds, who supplied firearms and ammunition linked to more than 100 crime scenes, including homicides.

However, inspecting tool marks in barrels is tricky for forensic examiners because the barrel is so narrow that no conventional cameras can be fitted down it to see said tool marks. Alternative options to investigate the barrel require dismantling the firearm which raises safety concerns and concerns over the preservation of accompanying evidence.

At the University of Huddersfield, we are currently researching how X-ray Computed Tomography (XCT) can aid in forensic investigations to overcome the issues of modified and converted firearms.

XCT has previously played a major role within forensics, being used mainly for post-mortem investigation, ranging from the measurement of cut marks in bone to the investigation of dismembered bodies found in suitcases.

The technology relies on the use of X-rays to penetrate the firearm and use the information gathered to build a 3D model. For this research, the principle is like that used in a hospital setting, however significantly higher power and resolution would be employed to ensure full reconstruction of dense materials.

The basic process would involve placing the firearm in the XCT machine, scanning it, and then reconstructing it into a 3D model with all inner geometries present, including the tool marks imparted by criminals on the inner barrel.

If these tool marks can be viewed and examined, it potentially means that they can be matched to the actual tool used and therefore lead to a conviction.

Should this research prove successful, it will mean that recovered firearms can be scanned still in the evidence bag, i.e., with no required handling or dismantling of evidence. As such, the evidence is fully preserved, and safety is maximised while still providing forensics with all information on the firearm.

As part of our research, we scanned and modified examples of barrels to determine what types of tool marks the XCT methods can reconstruct for forensic analysis.

Left: Inner of a British Small Arms (BSA) air rifle barrel; Right: Same BSA air rifle with the barrel drilled out

The preliminary results show that XCT can detect rifling and tool markings and reveal differences when the barrel has been modified such as in the second image where the British Small Arms (BSA) barrel had been drilled out.

XCT also offers examiners the ability to determine whether a firearm is still loaded or not with ammunition as can be seen in the images below.

XCT scan of firearm barrel with cartridge case still present

The hope is that this research, when complete, will give forensic examiners a full and detailed method to allow them to confidently scan and look at modified and converted firearms in a safe way whilst still preserving all evidence.

Currently, issues arise with bringing live modified and converted examples to the University to be scanned as there is strict legal requirements within the UK. However, we work closely with a firearms consultant and hopefully this will enable us to gain access to more examples.

Looking towards the future, the project aims to — by September 2022 — have created a Standard Operating Procedure (SOP) for firearm examiners that will enable any firearm examiner to follow the method and obtain results which are able to be used in a court setting.

Hannah Smith is a PhD Researcher within the Future Metrology Hub at the University of Huddersfield, UK.

Katie Addinall is a Lecturer within the Future Metrology Hub at the University of Huddersfield, UK. Her research began in 2013 in forensic ballistics investigating moving from 2D measurements to areal resulting in her PhD thesis “The application of advanced metrology techniques to ballistic tool mark investigation”. More recently she has been awarded the 2021 Beloe Fellowship to continue her research within forensic ballistics. Her profile can be viewed here.

Liam Blunt is a Professor and Director within the Future Metrology Hub at the University of Huddersfield, UK. Originating in material science throughout his career this has grown to include fields such as Tribology and Medical Implants, Development of Standards and Forensic Metrology for Ballistics. His profile can be viewed here.

Blog posts are intended as a way for various Small Arms Survey collaborators and researchers to discuss small arms- and armed violence-related issues, and do not necessarily reflect the views of either the Small Arms Survey or its donors.



small arms survey

Providing expertise on all aspects of small arms and armed violence.