Rule 601 - [Effective until 1/1/2025] Competency in General: Disqualification(a) General rule of competency. Every person is competent to be a witness except as otherwise provided by statute or in these rules. (b) Disqualification of witness. A person is disqualified to be a witness if the court determines that (1) the proposed witness is incapable of expressing himself concerning the matter so as to be understood by the judge and jury either directly or through interpretation by one who can understand him, or (2) the proposed witness is incapable of understanding the duty of a witness to tell the truth.