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 Utah, the regulation regarding Blood Alcohol Concentration (BAC) is more stringent than in most other states. While the standard for legal intoxication in many states is a BAC of .08 or higher, Utah has set its per se BAC level at .05. This means that a driver with a BAC of .05 or higher is presumed to be driving under the influence (DUI) by definition. For drivers under the legal drinking age of 21, Utah enforces a zero-tolerance policy, where any detectable BAC can result in a DUI charge. The state does not specify a higher threshold for aggravated or enhanced-penalty DUI based on BAC; however, penalties can be more severe for higher BAC levels or for repeat offenders.