A fire victim found in a smoke-filled room has COHb saturation of 65%. Autopsy shows soot in the trachea and bronchi, cherry-red lividity, and frothy exudate in the bronchi. Which finding MOST definitively establishes that the victim was alive during the fire (vital reaction)?
- A Soot in the trachea and bronchi ✓
- B COHb level of 65%
- C Cherry-red lividity
- D Absence of external burn injuries
Explanation
Soot in the trachea and lower bronchi definitively establishes that the victim was alive and breathing during the fire — a post-mortem victim would only show soot deposits in the upper airway and nasal passages from passive exposure. COHb elevation is the primary cause of death but does not itself prove vital reaction because post-mortem carboxyhaemoglobin formation can occur from ambient CO diffusing through skin into stagnant blood. Cherry-red lividity is a consequence of COHb and indicates CO exposure but is not a vital reaction marker per se. Histological evidence of acute inflammatory reaction (neutrophils) in the bronchial mucosa further confirms antemortem smoke inhalation.
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.