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blood alcohol concentration (BAC)

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 Texas, the legal limit for Blood Alcohol Concentration (BAC) for drivers aged 21 and over is .08%, in line with the majority of states. This means that a driver with a BAC of .08% or higher is considered legally intoxicated and can be charged with Driving While Intoxicated (DWI). For drivers under the age of 21, Texas enforces a zero-tolerance policy, where any detectable amount of alcohol can lead to a DUI (Driving Under the Influence) charge, reflecting the national zero-tolerance BAC level of .02 for underage drivers. Additionally, Texas has an enhanced penalty for drivers who are caught with a BAC of .15% or more, which is considered an aggravated DWI offense. These regulations are designed to discourage driving under the influence and to penalize those who do so more severely.

Legal articles related to this topic

The Blood Alcohol Content (BAC) Misconception: Why Being "Under the Limit" Doesn't Always Mean You're in the Clear
While your blood alcohol content (BAC) is a factor in determining DUI/DWI charges, simply being below your state’s limit does not mean that you’re legally in the clear.