The U.S. Court of Appeals for the Ninth Circuit is preparing to rehear a key equal pay challenge asking whether employers can use salary history as a reason to pay a woman less than a man for the same work.

Last April, the en banc federal appellate court ruled employers could not use past salary as a defense. Prior salary standing alone is not a “factor other than sex” under the Equal Pay Act, said the court, and such a factor must be job-related.

The case, Yovino v. Rizo, was appealed to the U.S. Supreme Court. But in February, the high court did not reach the merits of the Equal Pay Act claim. Instead, the justices, in an unsigned opinion, vacated the Ninth Circuit ruling because, they said, the en banc court was wrong to count the late Judge Stephen Reinhardt's vote when it filed its ruling.

The appellate court had said, in a footnote, that Reinhardt had “fully participated and authored this opinion. The majority opinion and all concurrences were final, and voting was completed by the en banc court prior to his death.”

But the high court said the Ninth Circuit's justification for counting Reinhardt's vote was “inconsistent with well-established judicial practice, federal statutory law, and judicial precedent.” Reinhardt, the “liberal lion” of the Ninth Circuit, died in March 2018.

The Ninth Circuit on Thursday announced that Judge Carlos Bea would replace Reinhardt on the en banc court in the Yovino case. No date has been set for rehearing arguments.

Jones Day partner Shay Dvoretzky, counsel to Fresno County Superintendent of Schools Jim Yovino, had questioned Reinhardt's participation in his Supreme Court petition. Dvoretzky argued, “When Judge [Stephen] Reinhardt died, he left 'regular active service' as a federal judge. So when the Ninth Circuit 'determined' this case or controversy, its en banc panel consisted of a judge not 'in regular active service' or otherwise eligible to participate.”

Representing Aileen Rizo, Daniel Siegel, a partner in Siegel, Yee & Brunner in Oakland, California, countered in his opposition brief: “Judge Reinhardt's 'participation' in this case occurred entirely during his lifetime. That the decision was not publicly announced prior to his death does not change its validity.”

Rizo claimed that the school superintendent paid her $10,000 less than male math consultants who performed exactly the same work.

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