The Supreme Court’s grant of review Thursday in People v. Frahs checks three different boxes for rare — but not unprecedented — occurrences.

First, the court ordered review on its own motion. That happens sometimes. The case initially went on the court’s docket when a non-party filed a request to depublish the Court of Appeal’s opinion.

Second, the court usually grants review in cases at one of its Wednesday conferences. No conference was scheduled for this week at all, however.

Third, a Court of Appeal justice — Fifth District Justice Jennifer Detjen — was assigned to the matter as a pro tem and joined just three other justices to reach the minimum number to grant review. To our knowledge, a pro tem justice has cast a deciding vote to grant review only one other time since Justice Kathryn Werdegar’s retirement left the court with a 16-month vacancy. As in Frahs, the previous pro tem voted with Chief Justice Tani Cantil-Sakauye and Justices Ming Chin and Carol Corrigan to grant review.

Thursday’s grant of review raises the question why a pro tem justice was appointed at all. On petitions for review, a pro tem is appointed to fill the vacancy only if “four justices cannot agree on a disposition,” according to the court’s Internal Operating Practices and Procedures. That was the case in Frahs. But, unlike the previous pro tem review grant, the court could have waited to rule on review until it was back at full strength. Joshua Groban will fill Justice Werdegar’s seat next week and the court extended until January 26 its time to order review on its own motion.

Shouldn’t the deciding vote whether to grant review in Frahs been cast by permanent Justice Groban instead of a temporary justice? Not necessarily. At the same time as its order in Frahs, the court also granted the petition for review in People v. Demedio (with the same pro tem casting the deciding vote), which is now on hold pending a decision in Frahs. In Demedio, the court’s time to rule on the petition for review expires Monday, three days before Groban is sworn in. Thus, without acting by Monday, the court would have lost jurisdiction to grant-and-hold in Demedio.

In Frahs, the court limited the issues to: “Does Penal Code section 1001.36 apply retroactively to all cases in which the judgment is not yet final? Did the court of appeal err by remanding for a determination under Penal Code section 1001.36?” Section 1001.36 allows pretrial diversion for certain mentally disordered defendants. The published opinion of the Fourth District, Division Three, in Frahs held the statute is retroactive and directed the superior court to conduct a diversion eligibility hearing.