In Arnold v. State, 853 S.W.2d 543, 544 (Tex. Crim. App. 1993), this Court made Rule 18a applicable to criminal cases. Rule 18b(2) states that a judge shall recuse himself in any proceeding in which: (a) his impartiality might reasonably be questioned; (b) he has a personal bias or prejudice concerning the subject matter or a party, or personal knowledge of disputed evidentiary facts concerning the proceeding; (c) he or a lawyer with whom he previously practiced law has been a material witness concerning it; or (d) he participated as counsel, advisor or material witness in the matter in controversy, or expressed an opinion concerning the merits of it, while acting as an attorney in government service.