Blood Alcohol Concentration (BAC) refers to the percent of alcohol (ethyl alcohol or ethanol) in a person’s bloodstream and is usually determined by a breathalyzer test or a blood test when the police suspect a driver of being intoxicated. For example, a BAC of .10% means that the person’s blood supply contains one part alcohol for every 1,000 parts blood.

In most states a driver is considered legally intoxicated if their BAC is .08 or higher. This BAC level is generally prescribed by a state statute (a law enacted by the state legislature) and creates a presumption of intoxication—also known as per se BAC because it is intoxication by definition. In Utah, the per se BAC level is .05.

Most states have a zero-tolerance BAC level of .02 for drivers under the legal drinking age (usually 21) that will result in a DUI/DWI charge. And most states also have an enhanced penalty or aggravated DUI/DWI charge for drivers whose BAC is .15 or higher—with a few states placing this aggravated or enhanced-penalty DUI/DWI BAC level at .16 to .20.

In Louisiana (LA), the regulation regarding Blood Alcohol Concentration (BAC) aligns with the majority of states in that a driver is considered legally intoxicated if their BAC is .08% or higher. This level of BAC creates a presumption of intoxication, known as per se intoxication, meaning that a person with a BAC at or above this threshold is intoxicated in the eyes of the law without the need for further evidence. For drivers under the legal drinking age of 21, Louisiana enforces a zero-tolerance policy, where a BAC level of .02% or higher can result in a charge of Driving Under the Influence (DUI). Additionally, Louisiana imposes enhanced penalties for drivers who are caught with a BAC of .15% or higher, categorizing such offenses as aggravated or enhanced-penalty DUIs. These regulations are set by state statutes and are enforced to promote road safety and deter impaired driving.