Fire deaths – a review and an experimental investigation of post-mortem formation of carboxyhaemoglobin

Abstract

The forensic investigation of deceased retrieved following a fire includes determining if death occurred before or during the event. A blood carboxyhaemoglobin level above 10% is considered indicative of respiration during a fire, implying that an individual was not deceased before the event. Previous spectroscopic studies have revealed that oxygen can passively diffuse through the skin and re-oxygenate haemoglobin. It was therefore questioned if carbon monoxide could also dermally diffuse and elevate post-mortem blood carboxyhaemoglobin levels, which could falsely insinuate that an individual had been alive and respired during a fire. Exposing both oxygenated and deoxygenated forms of haemoglobin to carbon monoxide converted them to carboxyhaemoglobin. This was measured using an ISP-REF Integrating sphere coupled to a USB spectrometer by fibre optic probe. Stillborn piglets were exposed to carbon monoxide to show that the gas can passively diffuse through the skin, resulting in formation of carboxyhaemoglobin in hypostasis, which was confirmed by observing a shift in the absorption spectrum. Piglets with significant cavity breaches, as could be found in cases with extensive stab/bullet wounds or heat defects, exposed to carbon monoxide demonstrated cavity carboxyhaemoglobin levels above 10% which could falsely suggest respiration of carbon monoxide had occurred.