Albany State forensic scientist details laboratory techniques for gunshot‑residue analysis

Doctor Zachariah Ullman, director of the forensic science program and professor of forensic science at Albany State University in Albany, Georgia, described laboratory approaches to identifying and interpreting gunshot residue (GSR) in a technical presentation. "The product of firearm discharge is called gunshot residue," Ullman said, and he said analyzing that residue can help reconstruct aspects of a shooting.

Ullman framed the talk around three laboratory techniques his team uses: scanning electron microscopy with energy‑dispersive X‑ray spectroscopy (SEM/EDS), time‑of‑flight secondary ion mass spectrometry (TOF‑SIMS), and X‑ray photoelectron spectroscopy (XPS). "In the analysis of GSR, I talk about 3 instruments, scanning electron microscope, time of light secondary ion mass spectrometer, X‑ray photo electron spectrometer," he said, then summarized the reconstruction workflow as collect, analyze and interpret evidence in relation to the case.

Why this matters: Ullman said GSR can indicate shooter distance, whether a wound occurred while the victim was alive, whether a shot passed through clothing, and can support cartridge identification. "You can determine the distance of the shooter from the victim," he said, and added that color and distribution of residues can provide investigative clues.

What each technique does: Ullman described SEM/EDS as a method to image particle morphology and identify elemental composition; analysts look for bright, often spherical inorganic particles that contain elements such as lead, barium and antimony. He said SEM specimen preparation commonly includes sputter‑coating samples with a thin gold layer to improve image clarity and that EDS spectra and colorized elemental maps make element distribution visible. "Here is the energy, EDS spectrum of the GSR component," he said, pointing out lead, barium and antimony peaks associated with primer constituents.

Ullman characterized TOF‑SIMS as providing mass information and spatial maps of chemical components and noted his lab does not own the instrument: "We hired it, in collaboration with the department of chemistry in the Georgia Institute of Technology Atlanta." He said TOF‑SIMS and sputtering can reveal whether elements appear in elemental or oxide form and how concentrations change with depth.

On XPS, Ullman described it as a surface‑sensitive technique that identifies elements and oxidation states by measuring the kinetic energy of electrons ejected by X‑ray bombardment. "It is qualitative [and] quantitative," he said, and that XPS can distinguish oxidation states — for example, differentiating titanium metal from titanium oxide.

Examples and results: Ullman presented comparative images and spectra from SEM, TOF‑SIMS and XPS. He showed that, in his samples, lead and lead oxide concentrations were higher in the outer layer of a GSR particle and decreased after removing about 10 nanometers by sputtering, a pattern he said was consistent across techniques. He also cited an example involving a Remington .22 caliber sample, stating the same elemental components appeared across instruments.

Numbers and caution: During the talk Ullman cited national‑scale statistics on gun prevalence and firearm deaths; the transcript records those figures verbatim but with garbling (for example, a figure transcribed as "303 50000000"). The transcript‑recorded numbers are included here as stated by Ullman but are flagged as unclear and not verified in the record.

Ullman concluded by saying the techniques are complementary for multi‑component GSR work and invited questions from the audience. "SPS is a valuable complement technique for electron spectral studies," he said, and then asked whether there were any questions.

No formal actions or policy decisions were taken during the presentation; the session ended with a call for audience questions.