was deceased alive or dead at the time of the fire?
A blood sample (from anywhere in the body) must be taken for estimating the carboxyhaemoglobin (CO-Hb) level; this can be submitted to the hospital biochemistry department for an urgent CO-Hb level. Levels may be obtained ‘out-of-hours’ by obtaining an arterial blood gas syringe from A&E or ITU and running them through their blood gas analysers.
Smokers may have a CO-Hb level of up to 10% (although this could be as high as 20% in heavy cigar smokers), but a level of over 50% is good evidence that the deceased was alive at the time the fire started, and was able to breathe in the smoke and fumes generated by the fire. The CO-Hb level may be lower in those individuals more at risk of dying due to the effects of fire and smoke, such as the elderly, or those with chronic lung diseases.
A low CO-Hb level does not necessarily imply that the deceased was dead at the time the fire started; deaths due to a ‘flash-over’ fire are often associated with a ‘zero’ or ‘normal’ CO-Hb level.
The presence of soot in the airways, particularly below the level of the vocal cords, and mixed with mucous in the distal airways, is additional evidence supporting the view that the deceased was alive at the time the fire started. Always comment on the presence/ absence of soot in the trachea!
Source: Richard Jones (WIFM)
A careful external examination is required in order to identify any evidence of injury. Patterns of injury most in keeping with self-harm (such as incised wounds of the wrists, or old scars at ‘elective sites’ of self-harm etc), or assault (scalp lacerations etc) may point to an alternative cause of death, but an assessment of ante mortem injury may be complicated by the effects of fire, creating artefactual ‘injury’. For example, heat-induced splitting of the skin may resemble lacerations, but there will be no ‘vital reaction’ at the wound edges.
Other fire-related artefacts include;
- The ‘pugilist’ attitude – differential heat-related contraction of the limbs results in a characteristic position of the limbs; the arms are flexed at the elbows and wrists for example.
- Fractures – brittle fire-damaged bone may be fractured, particularly when such bone is crushed by collapsing building structures or damaged during the fire-fighting or recovery phases of the investigation.
- Extradural haemorrhage – heat-related extravasation of blood may collect in the extradural space, mimicking an extradural haemorrhage. The assessment of such an artefact may be complicated by the co-existence of a heat-related skull fracture in the same vicinity; if in doubt stop the post mortem and seek advice/ help!
- Pseudo-ligature marks – due to the effects of tight clothing/ jewellery and post mortem neck swelling.
- Anal dilatation.
Where the burning took place before death, there will be in the mouth and nose of the deceased a sooty-like ash; the hands and feet will be drawn up. If burning after death, although the hands and feet will be drawn up, there will be no ashes in the mouth ...
'Death by burning - to distinguish between bodies burnt before and after death', from the Hsi yuan lu (Instructions to coroners), originally compiled by Sung Tz'u. Translated by Giles HA and published in the Proceedings of the Royal Society of Medicine 1924; 17 (Section of the History of Medicine): 59-107
... a woman murdered her husband and thereafter set fire to the house so that it burned down, falsely stating that her husband had burned to death. Her husband's family suspected her, and accused her before the authorities. The woman denied, and would not confess her crime. Chang Chu then took two pigs. One he had killed, the other he let live. Then he had both of them burned in a shed on a heap of faggots. On investigating (the difference between the two burned pigs, he found that) the pig previously killed had no ashes in its mouth, while the mouth of the pig burned alive was full of them. Then it was verified that there were no ashes in the dead man's mouth. When she was confronted with this evidence, the woman indeed confessed.
In Parallel cases from under the pear tree (Thang Yin Pi Shih), Kuei Wan-Jung 1222 AD (Translated by van Gulik RH 1956)