Ariz. Rev. Stat. § 48-510
When all defendants to the condemnation action have answered, or have been served with summons and their default entered, the plaintiff or any defendant whose default has not been entered, may, upon five days notice to the parties, except defendants in default, move the court to set the action for trial. If, upon hearing the motion, a trial by jury or by the court without a jury is not demanded, the trial shall be deemed waived by all parties not so demanding, and the court shall appoint three disinterested persons as referees to ascertain the compensation to be paid to the defendants waiving trial. The referees shall be residents of the municipality where the improvement is to be made, and over the age of eighteen years, and shall take and file with the court an oath to discharge their duties faithfully and impartially. If a referee fails to qualify, resigns, is removed by order of court or is unable to act, the vacancy created shall be filled by the court.
A.R.S. § 48-510