Ariz. R. Crim. P. 19.4
If the judge who is hearing or trying a criminal proceeding becomes ill or is otherwise incapacitated, that judge may be replaced by another judge of the same court. If no other judge is available, the clerk or bailiff must recess the court and notify the presiding judge or, if unavailable, the Supreme Court Chief Justice, who will enter an order continuing the trial until selection of another judge to resume the proceeding. A court of appeals judge or a judge pro tempore may be appointed as a substitute. If the new judge believes after reviewing the record that continuing the proceeding would be unduly prejudicial, the judge must order a new trial or proceeding. The judge should consider the manifest necessity of declaring a mistrial over the objection of the defendant before ordering it.
Ariz. R. Crim. P. 19.4