The dermal nitrate (paraffin) test for gunshot residue on the hands of a suspect has largely been abandoned because:

• A It requires expensive equipment unavailable in most laboratories
• B It gives numerous false positives from common substances such as fertilisers, tobacco and cosmetics ✓
• C Residue is always absent if the suspect washed the hands
• D It detects only lead and ignores barium and antimony

Explanation

The dermal nitrate or paraffin test uses diphenylamine reagent to detect nitrates and nitrites, but these are widespread in fertilisers, tobacco, urine, cosmetics and many occupational materials, producing frequent false positives. It therefore lacks specificity and is not accepted as proof of firing. Modern practice relies on detection of particulate lead, barium and antimony by scanning electron microscopy with energy dispersive X-ray analysis.

Reference: Parikh's Textbook of Medical Jurisprudence, Forensic Medicine and Toxicology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.