Cracking the Case: How Police and Science Took Down a 3D Printed Gunsmith

It started with a tip in January 2022. Police in the West Midlands region of the UK launched Operation Captiva after receiving information that something suspicious was happening in one of the homes. Once inside, detectives uncovered more than they expected: hybrid 3D printed weapons, a functioning 3D printer, and a database of firearm blueprints.

What seemed like a normal investigation quickly turned into a key case. With the help of advanced imaging technology and university researchers, the evidence didn’t just hold up in court, it upgraded the charges and led to a conviction. The defendant, David Biddell-Portman, pleaded guilty to two counts of manufacturing a firearm and was sentenced to five years in prison in June 2023. Now, nearly two years after the initial raid, the case has resurfaced as the researchers involved have published a paper offering new insights into the challenges of combating 3D printed firearms used by criminals.

Picture taken at the scene showing the two exhibits submitted for micro-CT scanning, namely JRM-02 – Blank firing rifle with converted barrel and converted rounds (bottom), and JRM-03 – Mixture of 3D printed and real firearm parts (top). Image courtesy of the University of Warwick.

The Discovery

During the 2022 raid, officers uncovered what looked like a small arsenal inside one of Biddell-Portman’s bedrooms; they found two firearms with components made of plastic and metal. These were hybrid 3D printed guns, blending 3D printed plastic parts with metal components to create fully functional weapons.

Also at the home, officers found a Creality Ender Pro 3 3D printer, which can be bought online for less than £200. Alongside the printer, they discovered a digital collection of more than 2,400 files, all related to firearms and their components. There were blueprints for receivers, magazines, and other critical parts, as well as a step-by-step manual on how to assemble a semi-automatic carbine capable of firing 9 mm Luger ammunition, identified as FGC-9 MKII.

While the suspect claimed he was simply fascinated by firearm mechanics, the items in that room told a much darker story.

Picture taken at the scene showing the 3D printer (Creality Ender Pro 3 3D printer) that was found in a cupboard. Image courtesy of the University of Warwick.

The Weapons

The two weapons seized during the raid were labeled JRM-02, a hybrid firearm with components from an airsoft gun and 3D printed parts capable of firing modified ammunition, and JRM-03, which was the semi-automatic FGC-9 MKII. The JRM-03 had a 3D printed receiver and stock combined with metal parts for better durability.

According to the study titled The use of micro-CT in the investigation of a case involving 3D printed firearms, published in Forensic Science International, the mix of plastic and metal made these weapons more reliable than fully 3D printed guns. Researchers explain that fully 3D printed weapons tend to malfunction after just a few shots. The hybrids, on the other hand, are built to last longer and fire repeatedly. What’s more troubling, they were designed to be assembled discreetly using everyday materials and affordable consumer-grade technology, like the kind that can be purchased on online shopping sites. In fact, the 3D printer found at the scene, the Creality, costs less than a smartphone and is marketed for hobbies like making toys, like avatars or action figures, custom phone stands for desks, or art projects like sculptures.

Images of the 2D cross-section (at the red plane shown in the inset image) through the micro-CT scan of JRM-02 showing the internal components. Image courtesy of the University of Warwick.

For the officers, this was uncharted territory, so they turned to experts at the University of Warwick’s Forensic Centre for Digital Scanning and 3D Printing. The team of researchers used a technology called micro-CT scanning, which works like a super-powered X-ray machine. It creates highly detailed 3D images, allowing investigators to see inside the weapons without taking them apart.

This approach was a game-changer. While traditional methods of analyzing firearms involve dismantling them, which risks damaging necessary evidence, micro-CT scanning “preserved a digital twin of the weapons,” ensuring that investigators had a permanent record even if something went wrong during test-firing.

The Analysis

The scans revealed intricate details about the weapons. Researchers explained that JRM-02 used a “straight blowback mechanism” to fire .22-caliber ammunition. The firearm combined 3D printed and metal parts, with some components borrowed from airsoft weapons.

Meanwhile, JRM-03 was even more sophisticated. It was capable of firing 9mm ammunition and included features like a silencer and a detachable magazine. However, the digital scans showed flaws in its design, such as a malfunctioning ejector mechanism, which limited its ability to fire multiple shots.

What’s more, the scans didn’t just help investigators understand the weapons; they completely changed the legal case and allowed prosecutors to present stronger evidence in court. Initially, the suspect faced charges of possession of illegal firearms, but the detailed analysis provided by the micro-CT scans showed the suspect had the intention to manufacture weapons.

Right lateral views of the 3D volume-rendered micro-CT scan (top) and X-ray (bottom) of JRM-02. Image courtesy of the University of Warwick.

In fact, the suspect had the tools, materials, and knowledge to build firearms capable of causing significant harm. This evidence allowed prosecutors to upgrade the charges to manufacturing firearms, a much more serious offense under the UK’s strict Firearms Act 1968. This law controls who can own, make, or sell guns in the UK. It’s illegal to have or create a weapon without a license, and breaking the rules comes with serious penalties. The Act helps the UK keep gun crime low and is known for being one of the strictest gun laws in the world.

In Court

The visual evidence prepared by the researchers was a big part of the trial. Prosecutors used 3D animations and pictures from the micro-CT scans to show the judge and jury how the weapons were built and how they worked, including the complex multiple components and mechanisms within the firearms. The animations made it easy to understand how the parts fit together and why the guns were so dangerous.

Even the judge, who admitted to having no prior experience with this type of evidence, found the visual aids invaluable. The clarity and detail helped paint a clear picture of the suspect’s capabilities and intentions.

“The judge overseeing this case has also noted that throughout their career, they had no experience in dealing with this type of evidence,” explain the researchers. “This further highlights the need for detailed and clear visual imagery when presenting evidence, especially as it is a new territory for the courts as well, in terms of the type of firearms involved in this case and the type of evidence presented. The investigative team firmly believes that the high quality of the evidence presented, as illustrated by the micro-CT scans, was highly influential in the sentencing of the defendant.”

Well, the result was that the suspect was convicted of two counts of transferring and manufacturing firearms and was sentenced to five years in prison.

Image of the 2D cross-section (at the green plane shown in the inset image) through the micro-CT scan of JRM-03 showing the internal components. Image courtesy of the University of Warwick.

The Bigger Picture

With 3D printed gun files widely available online and often disguised as harmless objects to avoid detection, law enforcement agencies around the world are racing to keep up. In the UK, police have started updating their training programs to help officers identify 3D printed weapons on the spot. Meanwhile, researchers are exploring technologies like PrinTracker, which can trace 3D printed objects to the specific printer that made them.

The West Midlands case is a perfect example of how science and law enforcement can work together to tackle emerging criminal threats. The use of micro-CT technology didn’t just solve a crime; it set a new standard for investigating and prosecuting cases involving 3D printed weapons.