Driving while under the influence (DUI) and/or driving while intoxicated/impaired (DWI) are criminal driving offenses in all states. These offenses encompass dangerous driving impairment caused by alcohol, drugs, or other controlled substances. In states that only charge either DUI or DWI offenses, the two terms are often colloquially used interchangeably. In states that charge both offenses, DUI charges usually refer to cases of alcohol impairment, while DWI charges usually refer to cases of impairment by recreational or prescribed drugs. Some jurisdictions prohibit impaired driving across the entire state, while others limit the prohibition to public roadways and areas open to the public.
Law enforcement officers can ask drivers to undergo chemical testing of their breath, blood, or urine whenever the officer suspects the driver of impairment. This suspicion is usually triggered when an officer witnesses dangerous or erratic driving. Drivers can refuse chemical testing, but in most jurisdictions, such a refusal will result in an automatic forfeiture of driving licensure, since states typically require that a driver must implicitly consent to chemical testing in order to obtain a driver’s license. Testing and arrests for DUI and DWI can also occur at sobriety checkpoints set up by the police. The Supreme Court upheld sobriety checkpoint programs as constitutional in Michigan Dept. of State Police v. Sitz, holding that 4th Amendment concerns over seizure were outweighed by the degree to which the sobriety checkpoint advanced the public interest in road safety.
Most impaired driving offenses are charged after a breathalyzer or blood test indicates that a driver’s blood-alcohol content (BAC) is above the federal BAC limit of 0.08%. State law may enforce a lower legal BAC limit. Some states may pursue DUI/DWI charges at lower levels for drivers under the legal drinking age. Some states may also allow charges to be brought without chemical testing results, if there is a suspicion of impairment due to erratic or dangerous driving coupled with a failed field sobriety test.
[Last updated in November of 2022 by the Wex Definitions Team]