Overt act
In criminal law, an overt act is the one that can be clearly proved by evidence and from which criminal intent can be inferred, as opposed to a mere intention in the mind to commit a crime. Such an act, even if innocent per se, can potentially be used as evidence against someone during a trial to show participation in a crime. For instance, the purchase of a ski mask, which can conceal identity, is generally a legal act but may be an overt act if it is purchased in the planning of a bank robbery.
The term is more particularly employed in cases of treason, which must be demonstrated by some overt or open act in some jurisdictions. This rule and adopted by the United States in Article III, Section 3 of the United States Constitution, which provides that "No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court." In Cramer v. United States, the Supreme Court ruled that "every act, movement, deed, and word of the defendant charged to constitute treason must be supported by the testimony of two witnesses."
In some jurisdictions, a defendant cannot be convicted of criminal conspiracy without an overt act being proven.