DUI (driving under the influence), DWI (driving while intoxicated), and OWI (operating while intoxicated) are similar criminal offenses that involve the operation of a motor vehicle, electric vehicle, or sometimes an otherwise-powered vehicle—including boats, aircraft, and bicycles—by an operator who is under the influence of or intoxicated by alcohol or drugs. Per se (pronounced purr-say) intoxication is intoxication by definition—as defined in the state’s statutes by blood alcohol concentration (BAC) of .08 or more (.05 in Utah). And even if a person is not per se intoxicated, they may be intoxicated by not having the normal use of their mental or physical faculties (abilities), for example, and may be charged with a criminal offense.

In some contexts the terms DUI and DWI are used interchangeably, with some states using one term and other states using the other term to define what is essentially the same criminal offense. But in some states both criminal charges are available and there is a legal distinction between them.

For example, in some states with both criminal offenses, DUI is the criminal offense of operating a vehicle under the influence of prescription or recreational drugs, and DWI is the offense of operating a vehicle while intoxicated by alcohol. In some states DWI refers to per se intoxication when the driver’s BAC is above the threshold defined by statute—.08 (.05 in Utah)—and DUI is a criminal offense charged when the police officer believes the driver is under the influence of alcohol, despite the driver’s BAC being below the statutory threshold of .08. And in some states DUI is a separate offense for drivers under the legal age of drinking (21) who have some alcohol in their system, but less than a .08 BAC.

These and other similar alcohol-related operating offenses—including aggravated or enhanced forms of these offenses—vary from state to state in their definitions and potential punishments and are generally located in a state’s statutes—often in the penal code or criminal code.

In California, DUI (Driving Under the Influence) is the term used for the offense of operating a motor vehicle while impaired by alcohol or drugs. The state's legal limit for blood alcohol concentration (BAC) is .08% for drivers 21 years and older operating regular passenger vehicles. For commercial drivers, the limit is .04%, and for drivers under the age of 21, any detectable amount of alcohol (.01% or higher) can lead to a DUI charge under California's zero-tolerance law. While DUI generally covers both alcohol and drugs, there is no separate DWI (Driving While Intoxicated) offense in California. The state does, however, have laws against driving under the influence of drugs (DUID). Penalties for DUI offenses in California can include fines, license suspension, DUI school, and even jail time, with increased penalties for repeat offenders or if aggravating factors are present, such as causing injury. It's important to note that even if a driver's BAC is below .08%, they can still be charged with a DUI if their mental or physical faculties are impaired to the point where they can no longer drive like a sober person under similar circumstances.