At today’s crime scenes investigators routinely compare suspect firearms to projectile bullets and cartridge cases collected at the scene. They also use “tool mark methodology” to obtain specific clues. If a firearm is not collected, then the caliber and sometimes make can be determined from cartridges and projectiles. The discovery of gunshot residue can only indicate a shooting occurred. But what if it could tell us more?
The new goal: Pinpoint the exact model of gun or pistol used at a crime scene using only gunshot residue. Scientist Igor K. Lednev, with the Department of Chemistry, University at Albany, SUNY, is working to develop a more rapid and accurate method of tracing ammunition used in a crime.
LET: Why compelled to you find a way to trace ammunition used in crimes?
Lednev: The majority of my 25-year academic career I have been doing fundamental research; however, every time I see an opportunity to apply my knowledge and expertise to solve a practical problem, I always go for it.
LET: How does the proposed method work?
Lednev: [This method] uses vibrational spectroscopy (Ramen and Infrared) …to detect and identify gunshot residue. Gunshot residue particles are organic or inorganic. Inorganic particles originate from a primer and metallic components of the firearm, and organic residue are made mainly from the propellant. Currently only inorganic particles can be detected. Vibrational spectroscopy is the most selective spectroscopic technique. A vibrational signature reveals specific characteristics of all chemical components in the material. We are creating a multidimensional spectroscopic signature of gunshot residue, which we can be linked to specific ammunition.
Vibrational spectroscopy reports on a complete chemical composition of gunshot residue.
LET: What are some advantages to this method?
Lednev: We don’t need projectiles, bullets or cartridge cases (to identify specific ammunition). We can detect gunshot residue from green lead free ammo. Plus, this is less expensive than current methods.
LET: Did you encounter any surprises in your research?
Lednev: The main surprise was when we found that even a single, tiny, gunshot residue particle is sufficient to differentiate two or three different firearms or ammunition. We did a so-called blind test when we shoot various guns and collected just one particle from each discharge, and we could identify with practically 100 percent certainty from which gun the particles came from.
LET: Where do we go from here?
Lednev: In order to link gunshot residue particles to specific ammunition, we need to create a spectroscopic library of practically all major types of ammunition. It’s a big job…but there are already spectroscopic libraries for automotive paint, synthetic fibers…someone can [do this] for ammunition, too. It’s just a matter of time and money.
However there is one thing we can do now. If there is a suspect with a firearm and gunshot residue is collected from a crime scene, we can exclude this specific firearms ammo from having been used.
