Intoxication due to a defendant’s voluntary consumption of drugs or alcohol isn’t usually a defense to criminal charges—but if the intoxication was involuntary, it may be a defense on the basis that the defendant did not understand what he was doing or that what he was doing was wrong. And some states allow a defendant to assert a defense that his voluntary intoxication prevented him from forming the specific intent to commit the crime (attempted murder, for example). But this is a question of fact that the jury will usually determine.

The availability and definition of any defense to criminal charges based on the defendant’s voluntary or involuntary intoxication is usually located in a state’s statutes—often in the penal or criminal code.

In Wisconsin, voluntary intoxication is generally not a defense to criminal charges. The state's statutes do not provide for voluntary intoxication as a defense to general intent crimes. However, under Wisconsin law, voluntary intoxication may be considered when specific intent is an element of the crime. This means that if a defendant was so intoxicated that they could not form the specific intent required for a particular crime, such as attempted murder, this could potentially be a defense. Nevertheless, it is up to the jury to determine the facts of the case and whether the defendant's level of intoxication actually prevented the formation of specific intent. In contrast, involuntary intoxication can be a defense if the defendant can show that they were involuntarily intoxicated and, as a result, did not understand what they were doing or that it was wrong. The specifics of these defenses and their application would be found in Wisconsin's penal or criminal code and interpreted through case law.