WVU chemist takes aim at more accurate test for gunshot residue February 6th, 2013
How many times have you seen a case closed on television using a gunshot residue test? Given how frequently it pops up on cop shows, you would think the test is widely used and easy to interpret. On television and in movies, if the suspect has gunshot residue on their hands, they definitely fired the gun.
Surprisingly, current methods of gunshot residue analysis focus on detecting residues from the primer, the part of the cartridge case that ignites the powder, and this residue is easily lost or transferred from one surface to another through contact as simple as a hand shake or high five.
“Results from primer residue analysis alone, the test most frequently used to determine if someone has fired a gun in criminal cases, can be difficult to interpret. For example, a person may have primer residue on their hands or clothing, but it could have gotten there by other means than that person firing a gun,” Suzanne Bell, PhD, said.
Bell, an associate professor at West Virginia University in the C. Eugene Bennett Department of Chemistry, is currently researching more effective gunshot residue analysis methods with an $181,412 grant from the Research Triangle Institute, International.
“By focusing on the primer residue alone, the organic residues of the gunpowder are ignored,” Bell said. “These organic propellant residues are potentially a rich source of physical evidence.”
Currently, here are no widely accepted tests for the analysis of the organic components of gunshot residue. Bell’s method analyzes the primer residues as well as the organic propellant residues using existing commercial instrumentation already used at airports to screen for explosives. The goal is to combine both pieces of test data to answer more definitively and more quickly, “Did this person fire a gun in the last few hours?” The data is evaluated using statistical methods and neural networks which can be automated for rapid response in field situations like crime scenes or the battlefield.
Bell says that many of the organic components of gunshot residue cling to skin and some are actually absorbed through the skin in the same way drugs in time-release patches are absorbed. Because of this, the organic materials are less likely to be lost or transferred and as such, have the potential to provide a greater level of confidence when trying to determine if a person has or has not recently fired a weapon.
When the trigger of a gun is pulled, the particulate primer residue along with vaporized organic materials from the propellant condenses, with significant amounts ending up on the shooter’s hand. By taking swabs of people’s hands, Bell can test for the organic materials on the surface of the skin or those that may have been absorbed into the skin.
“When complete, this research will help law enforcement and military personnel more definitively determine if a suspect has fired a gun recently,” Bell said.
Bell is conducting her research at Oglebay Hall, the WVU Crime Scene House Complex and local firing ranges with students in the WVU Forensic and Investigative Science Program.
Suzanne Bell received her doctorate in chemistry at New Mexico State in 1991 and joined the Mountaineer family in 2003. She is a member of the American Academy of Forensic Sciences and a fellow of the American Board of Criminalistics in the area of forensic drug analysis.
For more information, contact Suzanne Bell at 304-293-8606 or Suzanne.Bell@mail.wvu.edu