The justices 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.  Justice Sonia Sotomayor only agreed in the judgment.

The Ninth Circuit 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.”

Jones Day partner Shay Dvoretzky, counsel to Fresno County Superintendent of Schools Jim Yovino, had questioned Reinhardt's participation in his petition for review. “If a judge dies after argument but before the case is decided, may his vote continue to be counted?” asked the petition.

“When Judge [Stephen] Reinhardt died, he left 'regular active service' as a federal judge,” Dvoretzky argued in the petition. “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, partner in Siegel, Yee & Brunner in Oakland, California, countered in his opposition brief: “The premise of petitioner's second question is that a 'deceased judge' somehow 'continued to participate in the determination' of this case after he died. This premise defies reason. 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.”

The Ninth Circuit ruled that prior salary standing alone is not a “factor other than sex” and such a factor must be job-related under the Equal Pay Act, or EPA. The Equal Employment Opportunity Commission filed an amicus brief supporting  Rizo in the appellate court.

Employers long have argued that an applicant's prior salary history falls under the “catchall” category of “factor other than sex.” But the circuit courts vary widely in their treatment of salary history, according to Dvoretzky.

Urging the justices to resolve the circuit differences, Dvoretzky wrote in his petition: “In the Ninth Circuit, prior pay may not be used 'alone or in combination with other factors'; in the Second and Sixth Circuits, prior pay alone might suffice, so long as the employer has a good reason for relying on it; but in the Tenth and Eleventh Circuits, prior pay may be used, though only together with other factors.”

Siegel countered that the county schools superintendent paid Rizo $10,000 less than it paid male math consultants who performed exactly the same job.

“Its sole defense is that it set her lower salary based on the wages she earned for a different job before it hired her,” argued Siegel. “Contrary to petitioner's argument, there is not a single circuit in the Nation that would accept this barebones justification as an affirmative defense to an Equal Pay Act claim.”

The Tenth and Eleventh circuits previously held that prior pay alone cannot be considered an exemption to equal pay laws. The Seventh Circuit has ruled that salary history can be considered.

The U.S. Chamber of Commerce and the Society for Human Resource Management filed an amicus brief supporting Supreme Court review. “The Ninth Circuit's tortured reading of the EPA's 'catchall' defense also threatens the viability of a broad array of employment practices, such as individualized negotiation and competitive salary bidding, that include a reliance on prior pay,” wrote Jonathan Franklin of Washington, D.C.'s Norton Rose Fulbright US.

Read the court's ruling in Yovino v. Rizo: 

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