In all jurisdictions, driving while intoxicated (DWI) or driving under the influence of alcohol are serious offenses where the government tries to prove guilt by presenting what it considers to be objective scientific criteria. This usually occurs in the form of test results of an individual’s blood, breath or urine. Under the law, a score above a certain level is considered proof the individual drove drunk regardless of how clear-headed the individual perceives himself, or may actually be. The job of the attorney defending a DWI charge is to raise doubt about the legitimacy of the tests. For example, many DWI charges have been dropped (especially in the District of Columbia) because either the testing equipment was not properly maintained, or the police officer handling the equipment lacked the requisite credentials to perform the test.
Driving Under the Influence of Drugs or Alcohol (DUI) is charged where the government suspects the vehicle operator was drunk or impaired by drug use, but does not have scientific evidence to prove it. Usually the scientific evidence is lacking because the suspect chose not to submit to a breath, blood, or urine test, or because the equipment was not available.
Repeat offenders for DUI face greater penalties, often including mandatory jail time.