A person charged with drunk driving usually attacks the arresting officer's observations or opinions as part of his or her defense strategy. A defendant may also attack witnesses that tested the defendant's BAC, or the defendant may call on someone who can testify that the defendant was sober.

In addition to these strategies, a defendant could rely on one of several defenses. These defenses include the following:

(1) Necessity, which applies when a person must drive to prevent a greater evil;
(2) Duress, which applies when the defendant drives in order to avoid serious injury or death;
(3) Entrapment, which applies when an officer requests that a person drive drunk;
(4) Mistake of fact, which applies when a person has an honest belief that his or her BAC is below the legal limit;
(5) Involuntary intoxication, which applies when the person has ingested alcohol without his or her knowledge

Individual states take different positions with respect to the availability of these defenses. In general, however, these defenses rely on specific sets of facts and are each very difficult to prove successfully.