Final answer:
A co-conspirator's statement can be used at the trial of the other conspirator regardless of the circumstances.
Step-by-step explanation:
The admissibility of a co-conspirator's statement at the trial of the other conspirator is not dependent on being recorded on video, made under oath, or requiring the co-conspirator to testify. The statement can be used regardless of the circumstances as long as it meets the legal requirements. In the case of treason, the U.S. Constitution specifies that no person can be convicted of treason unless there is testimony from two witnesses to the same overt act, or a confession in open court.