FM13.16 | Toxic & War Gases — Summary & Reflection

KEY TAKEAWAYS

Toxic and war gases (FM13.16) are grouped by mechanism and forensic significance:

• Carbon monoxide: HbCO formation (200–300× O₂ affinity) + cytochrome oxidase inhibition → cherry-red PM findings; HbCO >50–60% fatal. Antidote: 100% O₂ (normobaric) or HBO (for severe cases — LOC, HbCO >25%, pregnancy). Pulse oximetry is unreliable — use co-oximetry.

• Cyanide (HCN): Complex IV inhibition → histotoxic anoxia; cherry-red PM (identical to CO visually); bitter almond smell; paradoxically high venous PO₂. Antidote: amyl nitrite → sodium nitrite → sodium thiosulphate; OR hydroxocobalamin (preferred in fire victims with co-CO exposure).

• MIC (Bhopal): alkylation of respiratory epithelium; no antidote; established corporate liability framework.

• Ammonia: upper airway corrosive; supportive care.

• CS/CN tear gases: TRPA1/TRPV1 agonists; reversible; rare deaths in enclosed high-concentration exposure.

Key PM distinction — CO vs cyanide: cherry-red in both; HbCO present in CO (absent in CN); venous PO₂ high in CN; bitter almond smell in CN; analytical tests confirm.

REFLECT

A family of six is found dead in their home on a cold winter night — a generator was running inside a closed room. As the forensic medicine officer called to the scene before the bodies are moved: describe your systematic approach to the scene examination before the post-mortem. What evidence would you document at the scene itself (source, ventilation, distribution of bodies) that will be impossible to reconstruct later? If the family owned an old generator and the landlord had been notified of ventilation problems three months ago, what legal implications might this have — and under which statute?