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Chapter: Forensic Medicine: Toxicology and alcohol

The role of alcohol in unnatural deaths

Analysis of the different deaths in this report emphasises the important role of alcohol in unnatural deaths.

The role of alcohol in unnatural deaths

According to the Fourth Annual Report of the National Injury Mortality Surveillance System 2002, the blood-alcohol concentration was determined in 11 927 of the 32 227 cases. The average blood-alcohol concentration was 0,18 ±0,1 g/100 ml (g%).

Analysis of the different deaths in this report emphasises the important role of alcohol in unnatural deaths. In 52,6% of the cases of manslaughter and murder a positive blood-alcohol concentration with an average level of 0,17 g% was observed. In 52,3% of all transport-associated deaths a positive level was found, with an average blood level of 0,19 g%. In 55,3% of all drivers a positive blood-alcohol concentration with an average of 0,17 g% was found. Approximately 60% of all pedestrians had a positive blood-alcohol concentration with an average of 0,22 g%.

Alcohol and violent death

In line with the findings of Le Roux and Smith, it has now become almost routine for blood to be drawn from the bodies of all persons over the age of 16 years who survived for less than 24 hours after a fatal injury.

During 1980 the blood of 1 617 bodies was sampled. Of these 1 510 had died a non-natural death, and blood-alcohol tests in respect of 61% were positive. An analysis of these deaths revealed that 41 persons had been driving at the time of the accident which had caused their deaths, and that they had died within one hour of the accident. Blood tests on 82% of them were positive, and 70% had been driving with a blood-alcohol concentration (BAC) in excess of 0,08%. Twenty-six per cent had probably been driving with a BAC which had rendered them 25 times more likely to cause an accident than when sober. Three of the 41 who had taken no alcohol were involved in accidents in which the other driver had a BAC in excess of 0,15%.

Alcohol tests in respect of more than half the passenger fatalities and 62% of pedestrian deaths were positive. In most cases levels were in excess of 0,20%. About 73% of the 424 persons stabbed to death and about 63% of the 180 kicked or beaten to death had high blood-alcohol levels at the time of death. In the case of the 61 drownings, 36 asphyxiations, and 128 firearm fatalities 62%, 50%, and 38% respectively were positive when tested for alcohol. The findings for the other unnatural deaths were not significantly different.

Follow-up findings for the subsequent five years presented an essentially similar picture.

Alcohol in drowning

a Possible factors leading to drowning

While the role of alcohol in the morbidity and mortality associated with motor-vehicle and other accidents is virtually exclusively due to its effects on the central nervous system, additional harmful physiological results couldensue in water. The effects of alcohol on the central nervous system must certainly be accepted as one of the ways in which alcohol plays a role in drowning.

There can be little doubt that when a person under the influence of alcohol disregards pleas not to enter rough seas, alcohol not only influences his decision to take such action but also reduces his awareness of the care required to prevent an accident, and, finally, his capacity to save himself once he is in difficulty.

Although the effects of alcohol on the central nervous system have been documented very thoroughly, there is much less clarity regarding the effects of alcohol on the cardiovascular system and temperature-regulating mechan-isms of an immersed human body. Intoxicating doses produce a rise in pulse rate, a fall in blood pressure, and cutaneous vasodilation with loss of body heat and a fall in body temperature. The skin temperature rises and the individual temporarily feels comfortably warm, even in cold surroundings. The increase in skin temperature leads to an increase of the gradient between the skin and the environmental temperature, thus causing hypothermia to develop.

The thermal conductivity of water is about 1 000 times greater than that of air at comparable temperatures. Alcohol ingestion and cold water immersion should therefore produce an even more significant fall in body temperature. There is little doubt that swimming hastens a fall in body temperature, so that hypothermia develops more readily, and this in turn significantly hampers swimming.

Exercise taken in the cold by normally healthy volunteers after the consumption of only 25g alcohol showed a fall in the mean blood-glucose concentration to 1,77 mmol/l. This was not observed when the same amount of exercise was done without alcohol consumption. Therefore, any person exercising strenuously in water while under the influence of alcohol could develop hypoglycaemia that can lead to paralysis.

Alcohol therefore not only has an impact on the central nervous system but probably also on the cardiovascular system and on glucose metabolism. All of these facts must, we believe, be regarded as significant (either individually or together) in a case of drowning.

 

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