Chemistry

• Alcohol, a simple sugar, exists in several forms. Ethyl alcohol, or ethanol, can lead to intoxication when consumed, and alcoholic beverages contain varying concentrations of ethanol. Other forms of alcohol, such as ethylene glycol, cannot be consumed because they can cause serious toxic reactions or even death.
  
  

Ingested Alcohol

• Alcohol passes through the stomach to the small intestine, from where it enters the bloodstream and travels to the brain. The liver, which processes chemicals and eliminates toxins from the body, removes about 95% of the alcohol from the bloodstream, with the rest exiting through breath, saliva and excretion. As the alcohol reacts with oxygen, it changes into a chemical called acetaldehyde, which then transforms again into acetic acid, finally exiting the body as carbon dioxide and water.
  
  

Bacterial Synthesis

• When someone dies, the body produces ethanol as a product of decomposition. The production of ethanol within the body begins shortly after death. As the body begins to decay, bacteria grow. The bacteria produce ethanol by converting it from sugars such as glucose. The ethanol levels rise as the body decomposes and the bacteria continue to reproduce, with concentrations approaching 1,500 mg per liter mere days after death.
  
  

Distribution

• Alcohol distributes itself through the body unevenly after death. The difference in water content among various body fluids and tissues causes alcohol to appear in higher or lower levels. Blood plasma, for example, has higher water content than whole blood, so it may show a 10 percent to 15 percent higher alcohol level. The gel-like substance inside the eye known as the vitreous humour, on the other hand, seems to collect little or no postmortem alcohol. Measuring the alcohol content in this fluid can, therefore, give the medical examiner a better idea of the pre-death alcohol level.
  
  

Considerations

• If the deceased person was involved in an accident or caused an event that injured or killed others, experts must take care to either confirm or rule out intoxication as a factor. Because alcohol production in the body after death is chemically the same as that from drinking, blood-alcohol content alone cannot determine whether the person consumed alcohol before death. The alcohol level of the person's urine may not give an accurate before-death picture either. The vitreous humour sample usually proves more useful in estimating intoxication, but in the end, the medical examiner must take into account the body's weight, age, sex, fat content, time of death and other factors.