The Locard exchange principle in firearm forensics is BEST applied when:

• A Calculating muzzle velocity from entry and exit wound dimensions
• B Estimating postmortem interval by wound healing at the entry
• C Reconstructing the trajectory using bullet path through barriers
• D Detecting primer residue (lead, barium, antimony) on the shooter's hand using SEM-EDX ✓

Explanation

Locard's exchange principle states that every contact leaves a trace—both ways. When a firearm is discharged, primer residue (gunshot residue, GSR) containing lead, barium and antimony is deposited on the shooter's hands, face and clothing, while bullet material may be exchanged with the target. Detection of GSR by SEM-EDX (scanning electron microscopy with energy-dispersive X-ray analysis) on the hands of a suspect is the classic application of Locard's principle in ballistics forensics. Trajectory reconstruction and PMI estimation are different forensic techniques.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.