Impossibility Defense - Legal Impossibility

Legal Impossibility

An act that is considered legally impossible to commit is traditionally considered a valid defense for a person who was being prosecuted for a criminal attempt. An attempt is considered to be a "legal" impossibility when the defendant has completed all of his intended acts, but his acts fail to fulfill all the required in elements of a crime in common law. Mistakes of law have proved a successful defense. An example of a failed attempt of law is a person who shoots at a tree stump, believing that he is committing attempted murder; that person cannot be prosecuted for attempted murder as there is no manifest intent to kill by shooting a stump. The underlying rationale is that attempting to do what is not a crime is not attempting to commit a crime.

However, "legal" and "factual" mistakes are not mutually exclusive. A borderline case is that of a person who shot a stuffed deer, thinking it was alive as was the case in State v. Guffey, (1953) in which a person was originally convicted for attempting to kill a protected animal out of season. In a debatable reversal, an appellate judge threw out the conviction on the basis that it is no crime to shoot a stuffed deer out of season.