Gunshot residue (GSR) analysis by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) is considered positive when particles containing which elemental combination are found?

• A Lead, antimony, and barium together in a single particle ✓
• B Lead alone in particles >1 micron diameter
• C Carbon and nitrogen in an organic matrix
• D Copper and zinc in a brass alloy particle

Explanation

Classic GSR particles contain a unique combination of lead (Pb), antimony (Sb), and barium (Ba) that co-localise in a single spherical particle generated by primer combustion in conventional ammunition. Finding all three elements together in a single particle is considered characteristic (unique) GSR by ASTM/ENFSI standards. Lead-only particles or copper-zinc particles are common background contaminants without forensic specificity. The introduction of lead-free ammunition changes the elemental signature but tri-element particles remain the gold standard.

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.