Most states have a zero-tolerance (or near zero-tolerance) blood alcohol concentration (BAC) level of .02 for drivers under the legal drinking age (usually 21) that will result in a DUI/DWI charge. Some states set the BAC level at which a minor may be charged with DUI/DWI at .05. And some states will charge a minor driving a vehicle with a BAC of less than the state’s per se intoxication level (usually .08) with violating a zero-tolerance law such as driving while ability impaired (DWAI)—but will charge a minor with a BAC of .08 or more with per se (pronounced purr-say) DUI/DWI based on the state’s BAC-level definition of intoxication—or, in the absence of a chemical test of blood, breath, or urine, will charge the minor with common law DUI/DWI based on the police officer’s belief the minor was driving while intoxicated.

DUI/DWI criminal offenses, punishments, and terms used for underage DUI/DWI vary from state to state. These laws are generally located in a state’s statutes—often in the penal code or criminal code.

In Kentucky, the state adheres to a zero-tolerance policy for underage drinking and driving. The legal drinking age is 21, and for drivers under this age, Kentucky law sets the blood alcohol concentration (BAC) limit at 0.02 for driving under the influence (DUI) charges. If an underage driver is found operating a vehicle with a BAC of 0.02 or higher, but less than 0.08, they can still be charged with DUI. For those with a BAC of 0.08 or above, the charge is the same as for adults—per se DUI, based on the state's definition of intoxication. Additionally, if there is no chemical test available, an officer's observation of impairment can lead to a DUI charge based on common law. The specific offenses, penalties, and terminology for underage DUI in Kentucky can be found in the state's statutes, which include the penal code and criminal code.