Yesterday’s Supreme Court conference was the first since Justice Martin Jenkins’s retirement. When the court is not at full strength, the court will call on Court of Appeal justices to sit pro tem for cases that are scheduled for argument, as it did for the November calendar cases. (But a short-handed court will normally not schedule a case for argument in the first place if the justices are tentatively evenly split on a decision. (See here.)) Things are different for conferences.
A short-handed court doesn’t call on pro tem justices at conferences unless the court is one vote short of the necessary four to grant review. The court’s Internal Operating Practices & Procedures explains:
When a justice is unavailable or disqualified to participate in a vote on a petition for review or other matter . . . and four justices cannot agree on a disposition, the Chief Justice, pursuant to constitutional authority (Cal. Const., art. VI, § 6), assigns in alphabetical order (except as set forth below) a Court of Appeal justice as a pro tempore justice to participate in the vote on the petition or matter. The assigned justice is furnished all pertinent petitions, motions, applications, answers, briefs, memoranda, and other material. A newly appointed Court of Appeal justice will be assigned as a pro tempore justice of the Supreme Court only after he or she has served on the Court of Appeal for one year. If a Court of Appeal justice is unable to serve on a particular case, the next justice on the alphabetical list will be assigned, and the Court of Appeal justice who was unable to serve will be assigned in the next case in which a pro tempore appointment is required.
(Emphasis added.)
Has a pro tem justice ever cast a deciding vote to grant review? Yes, but it’s quite rare.
