The issue of the defendant’s mental capacity to proceed shall be determined by the court in a contradictory hearing. The report of the sanity commission is admissible in evidence at the hearing, and members of the sanity commission may be called as witnesses by the court, the defense, or the district attorney. Regardless of who calls them as witnesses, the members of the commission are subject to cross-examination by the defense, by the district attorney, and by the court. Other evidence pertaining to the defendant’s mental capacity to proceed may be introduced at the hearing by the defense and by the district attorney.