Wetzel’s Research Delves into Often Asked Question About Gunshot Residue

Posted on August 10, 2016

Gunshot residue (GSR) is important evidence that can place a person at the scene of a crime with the smoking gun—literally—or prove someone’s innocence. Some questions, however, can completely undermine the results of GSR tests.

Dr. Stephanie Wetzel, left, and researcher Leah Ali MS’15 analyze samples during their study.

At Duquesne, Dr. Stephanie Wetzel is conducting research to determine the answer to one of the most often asked GSR questions—with regards to secondary transfer, could the GSR have gotten on a suspect’s hands by means other than actually firing or being in the vicinity of a fired gun? An assistant professor of chemistry and biochemistry in the Bayer School of Natural and Environmental Sciences, Wetzel and her team of student researchers have focused on GSR transfer from police officers, police vehicles and stations.

As part of the research, student volunteers were handcuffed, placed in a police car and then tested to determine whether any GSR had been transferred onto them. The team used two methods of GSR detection. SEM-EDS is used to identify characteristic primer residues, which include barium, lead and antimony. LC-MS/MS is used to identify organic gunpowder residues.

Wetzel’s work has shown that while GSR transfer is possible, it is minute in these scenarios. The research also indicated that it is possible to extract and detect GSR after an aluminum carbon-coated adhesive pad has been analyzed using the SEM/EDS detection method. This finding, Wetzel said, opens new doors for the future of GSR testing because analysts will be able to test the same sample using both the SEM/EDS and LC-MS/MS methods.

“It is important to understand GSR and its transfer to acquire accurate information from a crime scene and suspects,” said Wetzel.

Wetzel and her research team are currently conducting a number of other GSR-related studies, including:

  • Transfer during handcuffing by a police officer who has just discharged a firearm
  • Home loaded ammunition and variations in gunpowder GSR
  • Handshake transfer
  • How fast GSR settles to the ground once a weapon has been fired.

Wetzel’s current findings will be published in the September edition of the Journal of Forensic Sciences in an article titled A Study of the Presence of Gunshot Residue in Pittsburgh Police Stations using SEM-EDS and LC-MS/MS.

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