Test introduced to recover fingerprints from fired bullets

Scientists successfully achieve forensics’ “Holy Grail” by recovering fingerprints from ammunition casing  

A team of Irish scientists at Maynooth University has developed a ground breaking electrochemical technique which can recover fingerprints from fired brass ammunition casings, something long considered impossible due to the heat and friction of gunfire. A new electrochemical test can recover fingerprints from fired ammunition, even after extreme heat exposure. The method could greatly expand forensic capabilities. Researchers at Maynooth University have achieved a forensic milestone by introducing this process. The method uses mild voltage and non-toxic materials to make hidden ridges visible within seconds. Effective even on aged casings, it could help investigators connect evidence directly to a suspect rather than just a weapon.

Two Irish scientists have created a method for recovering fingerprints from fired bullet casings, something long believed to be impossible. Dr. Eithne Dempsey and her former PhD student, Dr. Colm McKeever, from the Department of Chemistry at Maynooth University in Ireland, have designed a novel electrochemical process which reveals fingerprints on brass casings even after exposure to the intense heat generated when a gun is fired. “The Holy Grail in forensic investigation has always been retrieving prints from fired ammunition casings,” said Dr. Dempsey. “Traditionally, the intense heat of firing destroys any biological residue. However, our technique has been able to reveal fingerprint ridges that would otherwise remain imperceptible.”

For decades, forensic experts have struggled to retrieve fingerprints from firearms or ammunition. The extreme temperatures, gas and friction produced during gunfire typically destroy any biological residue. Because of this, many criminals have relied on the assumption that fired weapons and casings could not link them to a crime scene. The research has significant implications for criminal investigations, where the current assumption is that firing a gun eliminates fingerprint residues on casings. “Currently, the best case of forensic analysis of ammunition casings is to match it to the gun that fired it,” said Dr. McKeever. “But we hope a method like this could match it back to the actual person who loaded the gun.” The team focused specifically on brass ammunition casings, a substance which has been traditionally resistant to fingerprint detection and is the most common type of material used globally. The research team discovered that coating brass casings with a thin layer of specially chosen materials can expose hidden fingerprint ridges. Unlike many existing forensic methods, this approach does not rely on toxic chemicals or expensive, high-powered equipment. Instead, it uses environmentally friendly polymers and requires very little energy to produce clear fingerprint images in seconds.

The researchers believe that the test for fingerprints on brass they have developed could be adapted for other metallic surfaces, expanding its range of potential forensic applications, from firearm-related crimes to arson. The process works by placing a brass casing inside an electrochemical cell filled with a chemical solution. When a low electrical voltage is applied, the chemicals are drawn toward the surface, filling the tiny gaps between fingerprint ridges and forming a distinct, high-contrast image. The result appears almost instantly. "Using the burnt material that remains on the surface of the casing as a stencil, we can deposit specific materials in between the gaps, allowing for the visualisation," said Dr. McKeever. “With this method, we have turned the ammunition casing into an electrode, allowing us to drive chemical reactions at the surface of the casing,” said Dr. McKeever. Tests showed that this technique also worked on samples aged up to 16 months, demonstrating remarkable durability. The research has significant implications for criminal investigations, where the current assumption is that firing a gun eliminates fingerprint residues on casings.

The researchers discovered that by coating brass casings with a thin layer of specialized materials, they could expose hidden fingerprint ridges. Unlike traditional methods that rely on harsh chemicals or complex equipment, this new technique uses safe, easily accessible polymers and very little energy to produce visible prints within seconds. "Currently, the best case of forensic analysis of ammunition casings is to match it to the gun that fired it," said Dr. McKeever. "But we hope a method like this could match it back to the actual person who loaded the gun." The team focused specifically on brass ammunition casings, a substance that has been traditionally resistant to fingerprint detection and is the most common type of material used globally. The process involves immersing the casing in an electrochemical cell containing specific chemical compounds. When a small voltage is applied, the chemicals in the solution are drawn to the surface, depositing material between the fingerprint ridges and forming a sharp, high-contrast image. The print emerges rapidly, appearing almost instantly as if by magic.

“Using the burnt material that remains on the surface of the casing as a stencil, we can deposit specific materials in between the gaps, allowing for the visualization,” said Dr. McKeever. The researchers believe that the test for fingerprints on brass they have developed could be adapted for other metallic surfaces, expanding its range of potential forensic applications, from firearm-related crimes to arson. This technique uses a device called a potentiostat, which controls voltage and can be as portable as a mobile phone, making it possible to create a compact forensic testing kit. Although early results are promising, the new fingerprint recovery method will need further testing and validation before it can be used by law enforcement agencies around the world. The project, supported by Research Ireland and Maynooth University, represents a major step forward for global policing and criminal investigation. Tests showed that this technique also worked on samples aged up to 16 months, demonstrating remarkable durability. This technique uses a device called a potentiostat, which controls voltage and can be as portable as a mobile phone, making it possible to create a compact forensic testing kit. While promising, the new technology faces rigorous testing and validation before it could potentially be adopted by law enforcement agencies worldwide.