(a)Appointment. Upon the written motion of the grand jury, the court shall appoint an investigator or investigators to assist the grand jury in its investigative functions. Said investigator may be an existing investigating law enforcement officer who is presently investigating the subject matter before the grand jury.(b)Presence. Upon written motion of the grand jury, approved by the prosecutor, the court, for good cause, may allow a grand jury investigator to be present during testimony to advise the prosecutor. No grand jury investigator shall question any witness before the grand jury. A grand jury investigator shall not comment to the grand jury by word or gesture on the evidence or concerning the credibility of any witness but may testify under oath the same as other witnesses. Annotation Despite defendant's contention that unauthorized persons were allowed in grand jury room and proceedings were not kept secret, the alleged violations did not affect defendant's substantial rights. Petit jury's subsequent guilty verdict made alleged error in grand jury proceeding harmless beyond a reasonable doubt. People v. Cerrone, 867 P.2d 143 (Colo. App. 1993), aff'd on other grounds, 900 P.2d 45 (Colo. 1995).