The breakthrough that could change how we gather evidence
A team of chemists at Maynooth University has announced a novel forensic approach that could finally help investigators recover fingerprints from fired ammunition. Led by Dr Eithne Dempsey and supported by PhD student Dr Colm McKeever, the research proposes a practical way to visualise fingerprint ridges on brass cartridge casings—surface evidence that has long eluded traditional methods after the high temperatures and gases produced when a gun is fired.
The science behind the method
The core idea is to coat the brass casing with a thin layer of specialised materials and then employ electrochemistry to make the hidden ridge patterns visible. In brief, a brass casing is placed in an electrochemical cell and connected to a potentiostat, a compact device that controls voltage. A controlled, low voltage is applied, drawing specific chemicals in the solution toward the surface. These materials selectively coat the spaces between fingerprint ridges, creating a high-contrast image of the print where once there was only an apparently featureless metal surface.
Why this works on brass
Brass has historically resisted conventional fingerprint techniques, especially after arson or firearm discharge. The Maynooth team’s approach leverages coatings and targeted electrochemical deposition to reveal minutiae that would otherwise remain imperceptible. Unlike harsher chemical processes or energy-intensive methods, the process uses non-toxic polymers and modest energy inputs, reducing risk to the operator and the scene.
From the lab bench to potential field use
One of the distinctive advantages highlighted by the researchers is portability. The potentiostat can be engineered to be compact—potentially as small as a smartphone—opening the possibility of a field-ready forensic kit. In principle, investigators could extract prints from brass casings recovered at crime scenes or in laboratories, with results available quickly enough to influence ongoing investigations.
How it could aid investigations
Traditionally, recovering fingerprints from ammunition has been viewed as a “holy grail” in forensics due to the destructive heat generated when firing. If validated, this technique could help link a suspect to ammunition directly used in a crime, or at least reduce the number of unknowns at a scene. Importantly, experts caution that, like any new method, it would be used in conjunction with other lines of evidence rather than as a stand-alone proof.
Validation, limitations, and next steps
The Maynooth study has been published in the forensic science journal Forensic Chemistry, detailing the initial proof-of-concept. However, the researchers emphasise that the technique must undergo rigorous testing and validation before it could be adopted by law enforcement agencies. Questions to address include reproducibility across different casings and brands, sensitivity under real-world contamination, the potential for false positives, and how well results hold up under various environmental conditions. Standardization of protocols and training for forensic practitioners will also be crucial in transitioning from laboratory success to field reliability.
Funding, collaboration, and broader impact
The work at Maynooth University has received support from Research Ireland and the university itself. The researchers say the approach could eventually extend beyond firearms. If adaptable to other metallic surfaces, it could broaden applications in areas such as arson investigation or other cases where metal objects bear traces of human contact, providing a new piece of the evidentiary puzzle for investigators.
A cautious path forward
As with any new forensic technology, careful validation is essential to ensure results are robust and defensible in court. The Maynooth team remains optimistic that, with further testing, the method could become a valuable tool in the forensic toolbox, complementing existing techniques and offering investigators a clearer view of who touched ammunition before it was fired.
