16. What is "blood-alcohol concentration" or "blood-alcohol level"?

Blood-alcohol concentration (BAC) is the level of alcohol in the bloodstream from drinking alcoholic beverages. BAC readings are used in court as evidence in drunk-driving cases. The most common method of measure is a breath test, although blood and/or urine testing is sometimes done. A result of .08 or higher may establish a presumption of intoxication. The details of the .08 BAC presumption laws vary among the states, but all 50 states have adopted .08 as their official intoxication level, in large part because of a federal threat of otherwise withholding highway funds.