Forensic Medicine · Trace Evidence and Crime Scene Reconstruction (Hair, Fibre, Glass, Paint, GSR)

Gunshot residue (GSR) analysis by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) identifies characteristic particles containing which triad of elements?

  • A Lead, barium, and antimony ✓
  • B Iron, copper, and tin
  • C Zinc, manganese, and nickel
  • D Chromium, cadmium, and molybdenum
Correct answer: A. Lead, barium, and antimony

Explanation

Classic GSR particles are spheroidal particles generated from primer components during firing. The three-element triad Pb-Ba-Sb (lead, barium, and antimony) is the characteristic signature of conventional primer compounds (lead styphnate, barium nitrate, antimony sulfide). SEM-EDX identifies these particles by their morphology (spheroidal, <10 µm) and elemental composition. Particles containing all three elements are considered characteristic GSR; two-element particles are consistent with GSR. Lead-free/green primers produce different elemental combinations (Zn-Ti-Sn), which has forensic significance.

Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.

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