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 Delaware, the Blood Alcohol Concentration (BAC) limit for drivers is consistent with the majority of states, where a driver is considered legally intoxicated if their BAC is .08% or higher. This is established by state statute and is known as a per se BAC level, meaning that a person with a BAC at or above this threshold is presumed to be driving under the influence (DUI) by definition. For drivers under the age of 21, Delaware enforces a zero-tolerance policy, where any detectable BAC of .02% or more can result in a DUI charge, reflecting the national trend towards strict enforcement for underage drinking and driving. Additionally, Delaware imposes enhanced penalties for drivers with a BAC of .15% or higher, which is considered an aggravated level of DUI and carries more severe consequences.