Cal. Civ. Proc. Code § 201

In any superior court, a separate trial jury panel may be drawn, summoned, and impaneled for each judge, or any one panel may be drawn, summoned, and impaneled by any one of the judges, for use in the trial of cases before any of the judges, as occasion may require. In those courts, when a panel of jurors is in attendance for service before one or more of the judges, whether impaneled for common use or not, the whole or any number of the jurors from such panel may be required to attend and serve in the trial of cases, or to complete a panel, or jury, before any other of the judges.