In T. P. B. v. Superior Court (1977) 66 Cal.App.3d 881, during a juvenile court hearing, the judge disqualified himself and declared a mistrial, explaining that he could not fairly and impartially consider the evidence. When a second hearing was set, the juvenile's plea of once in jeopardy was rejected on the ground that legal necessity warranted the mistrial. The appellate court affirmed, reasoning that once the judge admitted his disqualification, Code of Civil Procedure section 170 required that the action be heard by another judge. "The situation . . . did not involve a mere error of law or procedure; rather it involved the very jurisdiction of the trial judge to proceed with the action. The posture in which the action found itself is akin to the legal necessity deemed a physical cause beyond the control of the court brought about by the illness or absence of the judge." (66 Cal.App.3d at p. 886.)