Colorado Revised Statutes Title 13. Courts and Court Procedure § 13-72-102. Number of jurors

A grand jury shall consist of twelve persons, and the assent of nine jurors shall be necessary for the returning of a true bill; but, upon motion of the district attorney and for good cause shown, the court may cause to be convened, impaneled, and sworn a grand jury consisting of twenty-three members, and the assent of twelve members shall be necessary for the returning of a true bill when said grand jury consists of twenty-three members. At any meeting of the grand jury at least nine grand jurors shall constitute a quorum.