Fingerprints from Fired Bullet Casings: A Forensic ‘Holy Grail’ Comes Within Reach
The breakthrough
Researchers at Maynooth University (Ireland) have unveiled a lab-validated method that reveals latent fingerprints on fired bullet casings—evidence long thought to be destroyed by the extreme heat, friction, and gases of discharge. The technique uses a low-voltage, non-toxic electrochemical process to make hidden ridge detail appear on brass cartridge cases within seconds, and it has worked on samples aged up to 16 months. [ScienceDaily summary]
The work was published in Forensic Chemistry (DOI: 10.1016/j.forc.2025.100663) and summarized by ScienceDaily. Maynooth University also detailed the research and its implications in a university announcement. [Journal page] [University news release]
How the method works (in plain language)
Investigators place a brass casing into a small electrochemical cell—think of it like a controlled bath with specific chemicals. Applying a mild electrical voltage causes materials in the solution to deposit onto the casing’s surface between the fingerprint ridges that survived firing as microscopic “stencils.” The result is a high-contrast image of the print that can be photographed and examined. The equipment required (a potentiostat) can be compact and portable, opening the door to field-ready kits. [ScienceDaily summary]
Why this matters
Until now, the best most caseworkers could do with cartridge evidence was to link a recovered casing to the gun that fired it (via toolmark comparison). If robustly validated, this technique could sometimes link the casing to the person who handled or loaded the ammunition—potentially transforming leads in shootings and helping crack cold cases where the firearm isn’t recovered. [ScienceDaily summary]
What’s new vs. older approaches
Classical enhancement on metal (e.g., cyanoacrylate fuming + dyes, metal deposition) can struggle after discharge because biological residues are degraded. The Maynooth approach leverages post-firing residues on brass as a template and uses non-toxic polymers and low energy, rather than hazardous chemicals or bulky, high-power gear. That combination—speed, safety, simplicity, and age tolerance—is what makes this advance stand out. [ScienceDaily summary] [University news release]
Early performance highlights
- Speed: Visible ridge detail forms in seconds. [ScienceDaily summary]
- Aged samples: Successful visualization on brass casings stored up to 16 months. [ScienceDaily summary]
- Portability: Relies on a potentiostat that can be phone-sized, suggesting feasible field kits. [ScienceDaily summary]
Limitations and what validation will require
As with any new forensic method, operational adoption will hinge on inter-laboratory validation, error-rate studies, and defined quality-assurance protocols. Practitioners will want to know:
- How performance varies across ammo brands, surface finishes, and firing conditions.
- Effects of handling, cleaning, environmental exposure (rain, soil, heat cycles).
- Robustness of ridge detail for comparison (human/automated examiners), including metrics like clarity and distortion.
- Fit within evidence workflows and chain-of-custody. [University news release]
What comes next
The authors note potential to adapt the chemistry to other metals beyond brass, which could broaden use to additional firearm components—or even other crime-scene metals encountered in arson and explosives cases. Expect collaborative studies with police labs and blind trials before courtroom deployment. [ScienceDaily summary]
Key quotes from the researchers
- The team describes the recovery of prints from fired casings as a long-sought “Holy Grail” for forensic investigation. [ScienceDaily summary]
- They emphasize the aim of moving from matching Fel casing to a gun to, in some cases, matching it back to the person who loaded the ammunition. [ScienceDaily summary]
Bottom line for practitioners
A fast, low-hazard, electrochemical enhancement that reveals latent prints on fired brass could meaningfully change how cartridge evidence is used in investigations—provided it clears the necessary validation hurdles. If it does, labs may gain a new route to individual-level associations in shooting cases. [ScienceDaily summary] [University news release]
Source links
- ScienceDaily summary of the peer-reviewed study (with DOI): “Scientists achieve forensics’ ‘Holy Grail’ by recovering fingerprints from fired bullets” (November 2, 2025). https://www.sciencedaily.com/releases/2025/11/251102011206.htm
- Maynooth University news release with method details and context (September 30, 2025). https://www.maynoothuniversity.ie/news-events/mu-scientists-pioneer-breakthrough-fingerprint-forensic-test
Journal reference: Colm McKeever, Eithne Dempsey (2025). “Electrodeposition of redox materials with potential for enhanced visualisation of latent finger-marks on brass substrates and ammunition casings.” Forensic Chemistry, 44, 100663. DOI: 10.1016/j.forc.2025.100663.
