Blood Alcohol Content (BAC) Law and Legal Definition

Blood Alcohol Content or BAC is the amount of alcohol in a person’s body measured by the weight of the alcohol in a certain amount of blood. In short it is the concentration of alcohol in a person's blood. BAC is most commonly used as a metric of intoxication for legal or medical purposes. It is usually expressed in terms of volume of alcohol per volume of blood in the body. Breath analysis is the primary method used by law enforcement agencies to determine BAC, although a direct analysis of blood for this purpose is not uncommon.

There are state specific laws regarding the permissible extent of BAC in a person. State laws indicate levels of blood-alcohol content at which an individual is deemed to be under the influence of alcohol. Generally higher BAC levels can double the penalties under DUI laws.