FORENSICSForensics Lab Cracks Case on Newer, “Greener” Gunshot Residue

Discoveries by West Virginia University forensic scientists about how gunshot residue behaves on skin, hair and fabric will allow crime scene investigators to catch up to the proliferation of new, eco-friendly types of ammunition and make faster, more informed decisions at crime scenes and in forensic laboratories.

Lead and other toxic components of ammunition are crucial in establishing the presence of gunshot residue, or GSR, at crime scenes. However, heavy metals like lead aren’t present in new “green” ammunitions that are changing the rules for GSR analysis, according to Tatiana Trejos, associate professor in the Eberly College of Arts and Sciences Department of Forensic and Investigative Science.  

“A major forensics discovery was that, when you fire a gun, a cloud of particles is produced by the primer, the material that explodes and causes a bullet to eject. The primer contains, among other things, inorganic compounds, heavy metals like lead, barium, antimony,” Trejos said.

“When this cloud touches our skin, tiny particles remain there. The composition of those particles is specific to firearm discharge — we don’t commonly find that combination of metals in other conditions. That realization was a big help to forensic scientists in firearms-related investigations.”

But over the years, ammunition has changed. More primers are manufactured without metals harmful to the environment and human health. That’s a challenge for GSR analysis and the reason forensic science — a field that uses scientific methods to help solve crimes and examine trial evidence — is looking beyond inorganic compounds like metals to organic compounds like nitroglycerine that are also released when a gun fires.

“If we combine information about organic and inorganic compounds in GSR, we can have more confidence in our results,” Luis Arroyo, an analytical chemist and associate professor, said. “For over a decade, scientific groups have said we need to know more about organic gunshot residue. We’re missing opportunities to confirm the presence of GSR, and this research funded by the National Institute of Justice is helping to narrow that gap.”

The research establishes how organic and inorganic compounds in GSR differ in the ways they each persist on surfaces and transfer to other surfaces during activities like running, hand shaking or washing.

Trejos and Arroyo published the results of the studies in a Forensic Chemistry paper co-authored with WVU graduate students Courtney Vander Pyl, Kourtney Dalzell, Korina Menking-Hoggatt and Thomas Ledergerber.