Gunshot residue (GSR) analysis using Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy (SEM-EDX) detects characteristic particles. What is the SPECIFIC elemental composition of a 'unique' GSR particle that unequivocally confirms firing a weapon (conventional lead-based primer)?

• A Lead (Pb) alone
• B Barium (Ba) + Antimony (Sb) + Lead (Pb) in a single spherical particle ✓
• C Carbon + Nitrogen + Hydrogen composite
• D Copper (Cu) + Zinc (Zn) from bullet jacket

Explanation

GSR from conventional firearms with lead styphnate primers produce distinctive spherical or spheroidal particles containing a unique combination of Ba + Sb + Pb. A single particle containing all three elements in specific ratios (Ba-Sb-Pb triad) is considered a 'characteristic' GSR particle that is uniquely associated with firearm discharge. Particles containing only two elements (Ba-Pb, Ba-Sb, or Sb-Pb) are 'consistent with' GSR but not unique. Lead alone (A) is non-specific. Carbon-nitrogen (C) is from propellant combustion only. Copper-zinc (D) comes from bullet jackets and is non-specific for gunshot residue.

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

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Written and medically reviewed by the StethoPrep medical team.