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 Washington State, voluntary intoxication is generally not a defense to criminal charges. However, under Washington law, voluntary intoxication can be considered when determining whether the defendant had the capacity to form the specific intent necessary for certain crimes. This means that if a defendant was so intoxicated that they could not form the specific intent required for a crime like attempted murder, this may be used as a defense. On the other hand, involuntary intoxication can be a complete defense if it can be shown that the defendant was incapable of knowing what they were doing or that it was wrong due to the intoxication. The burden of proof for involuntary intoxication as a defense is on the defendant. The specifics of these defenses and their applicability are detailed in the Revised Code of Washington (RCW), particularly in the sections dealing with the state's penal code.