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 Iowa, voluntary intoxication is generally not a defense to criminal charges. However, under Iowa law, there are limited circumstances where voluntary intoxication may be considered as a defense. Specifically, if the crime charged requires a specific intent, voluntary intoxication may be used as a defense if it can be shown that the intoxication prevented the defendant from forming the requisite specific intent. This is most relevant in cases of serious crimes such as attempted murder, where intent is a key element of the offense. On the other hand, involuntary intoxication can be a defense if the defendant was coerced into consuming the substance or unknowingly ingested it, and as a result, lacked the capacity to understand the nature of their actions or to distinguish between right and wrong. The determination of whether intoxication can be used as a defense, and its impact on the defendant's state of mind, is typically a question for the jury to decide based on the facts presented at trial.