R.I. Gen. Laws § 11-43-2: Proof required for treason.

No person shall be convicted of treason against this state by levying war against the state, or by adhering to the enemies of this state, giving them aid and comfort, but by testimony of two (2) lawful witnesses to the same overt act for which he or she shall then be on trial, unless he or she shall confess it in open court.