Washington State DUI laws provide that the test of a DUI suspect’s alcohol level will be done by taking a sample of breath, and generally not blood. However, breath alcohol content and blood alcohol content can be different, especially when a person’s body temperature is elevated.
When one drinks, the alcohol is absorbed by the body and eventually gets into the bloodstream. That same alcohol gets into the breath of a person through the interaction of the lungs and the bloodstream. It is a well known fact, however, that body temperature affects how much alcohol is passed from the blood to the breath. For instance, if a DUI suspect drank enough beer to produce a blood alcohol reading of .07 (under the legal limit) you would think that the breath alcohol reading would be .07 as well. If the subject had a fever, however, the breath alcohol reading would be higher, perhaps over the .08 legal limit. This is not a theory but it is a scientific fact.