These cases are criminal in nature, although they can involve civil penalties, such as a suspension of driving privileges. DUI laws often include prohibitions against driving under the influence of controlled substances as well.

Most states prosecute drunk driving in three ways. First, a conviction can be based on the amount of alcohol in the defendant's blood, as measured immediately following the arrest. The legal limit in all states is currently .08%, with lower limits for commercial drivers and minors. This type of prosecution is called a "per se" DUI. It requires only that the state prove that a blood alcohol content test was administered, and that the result exceeded the legal limit.

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