All 50 states in the US and Puerto Rico now apply two statutory offenses to driving under the influence of alcohol. The first (and original) offense is known either as driving under the influence (DUI), driving while intoxicated/impaired (DWI), or operating [a motor vehicle] while intoxicated/impaired (OWI). This is based upon a police officer’s observations (driving behavior, slurred speech, the results of a roadside sobriety test, etc.)
The second offense is called “illegal per se”, which is driving with a Blood Alcohol Concentration (BAC) of 0.08 g/dL or higher. Since 2002 it has been illegal in all 50 states to drive with a BAC that is 0.08 or higher. Drivers are considered to be alcohol-impaired when their BAC is .08 or higher. Drivers with a BAC level of .08 or higher in fatal crashes were eight times more likely to have a prior conviction for driving while impaired than were drivers with no alcohol.