Alcohol Analysis in Urine and Other Body Fluids

Although blood alcohol concentrations are most commonly used to assess the degree of alcohol intoxication, blood is not always available for analysis, and it may be in poor condition, especially in postmortem investigations. Therefore, analysis of alcohol in other body fluids is common in forensic laboratories. The alcohol concentration in a body tissue or fluid is generally proportional to the water content of that tissue or fluid. For example, if the water content of a body tissue is 10% higher than that of blood, the tissue’s alcohol content should be 10% higher than that of blood. This is the basis for estimating blood alcohol concentrations from alcohol concentrations in other body fluids and tissues. Knowledge of the alcohol content of oral fluid, sweat, and tears can be used to make reliable estimates of coexisting blood alcohol concentrations. However, such estimates are more complicated when dealing with body fluids existing in isolated compartments where there is slow or very little exchange of alcohol between blood and the isolated fluid, for example, bile, eye fluid, and urine. Nevertheless, in postmortem investigations, knowledge of the alcohol content of any one of these and other fluids can often be used to estimate the minimum blood alcohol concentration existing some time before death.