Impossibility Defense

An Impossibility defense is a criminal defense occasionally used when a defendant is accused of a criminal attempt that failed only because the crime was factually or legally impossible to commit. Factual impossibility is rarely an adequate defense at common law. In the United States, thirty-seven states have ruled out factual impossibility as a defense to the crime of attempt. This is not to be confused with a 'mistake' of fact defense, which is always considered as a defense to criminal charges.