A team of Irish researchers at Maynooth University has developed a breakthrough electrochemical technique that can recover fingerprints from fired brass ammunition casings, something previously thought to be nearly impossible due to the high temperatures and friction generated during firing.
The new electrochemical test can even recover fingerprints after bullet casings have experienced extreme heat, which is expected to greatly improve forensic science's ability to handle cases. Dr Eithne Dempsey from the Department of Chemistry at Maynooth University and her former PhD student Dr Colm McKeever created the innovative technology to reveal fingerprint information on cartridge casings even after they have been exposed to the extreme heat of gunfire.
For decades, forensic experts have struggled to extract usable fingerprints from firearms and ammunition casings because the heat, friction and gases of firing destroy any biological traces. Criminals therefore often believe that leaving bullet casings behind will not be traced to the crime scene.
"Extracting fingerprints from fired cartridge casings has always been a 'Holy Grail' problem in forensic investigations," said Dr. Dempsey. "Conventional wisdom is that the high temperatures generated by the shot destroy any biological residue. Our technology can reveal those fingerprint ridges that would otherwise be invisible."
Researchers found that by covering the surface of brass cartridge cases with a special material, they could expose hidden fingerprint ridges. Unlike traditional methods that relied on powerful chemicals or complex equipment, this new technology uses safe and readily available polymers and uses very little energy to generate clearly visible fingerprints in seconds.
The specific operation is to immerse the cartridge case in an electrochemical bath containing specific chemicals. When a voltage is applied, chemicals in the solution are attracted to the surface of the cartridge case, depositing material between the ridges of the fingerprint, creating a high-contrast image. The fingerprint appears almost instantly, like "magic".
Dr. McKeever said: “Using the charred material remaining on the surface of the cartridge case as a template, we were able to deposit specific materials between the fingerprint ridges to achieve visualization.” Tests showed that the technology is still effective even after the sample has been stored for 16 months, showing extremely high durability.
This research is of great significance to criminal investigation. Currently, investigation departments generally believe that the cartridge case cannot retain fingerprint residue after being fired. Dr McKeever noted: "The current best result from forensic analysis of a cartridge casing is to match it to the firearm that fired it. We hope this new method can directly link the cartridge casing to the actual person who loaded it."
The research team focused on brass bullet casings, a material that has been extremely difficult to detect fingerprints in the past and is the most common bullet casing material in the world. Researchers believe that this fingerprint detection technology is expected to be extended to other metal surfaces, opening up wider forensic application prospects for cases related to firearms and arson.
The technology uses a device called a potentiostat to control voltage, which can be miniaturized to the size of a cell phone, potentially creating a portable forensic testing toolbox. Dr McKeever said: "With this approach we make the cartridge case itself the electrode, allowing chemical reactions to occur on its surface."
Experts emphasize that although this new technology is very promising, it still needs to undergo rigorous testing and verification before being promoted and applied by law enforcement agencies around the world. The relevant research paper was published in the journal "Forensic Chemistry" on April 19, 2025.
This research was supported by a PhD Teaching Scholarship from the Department of Chemistry, Maynooth University and an Irish Research Council PhD Scholarship.
Compiled from /ScitechDaily