For the first time in 16 years, the California Supreme Court has found that racial bias improperly tainted a jury selection, prompting the court to overturn three convictions — two for attempted murder.

The unanimous decision, written by Justice Mariano-Florentino Cuéllar, appeared intended to send a clear signal to prosecutors, defense lawyers and the lower courts that charges of racially motivated juror exclusions must be taken seriously.

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“It is not only litigants who are harmed when the right to trial by impartial jury is abridged,” Cuéllar wrote Thursday. “Taints of discriminatory bias in jury selection — actual or perceived — erode confidence in the adjudicative process, undermining the public’s trust in courts.”

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Thursday’s decision amounted to a strong statement that deference without careful examination no longer would be tolerated, though Cuéllar and Liu framed their views in ways not to offend conservatives.

Cuéllar focused more on the need to protect would-be jurors from discrimination than on the rights of criminal defendants.

“The mix of Californians who report for jury service across the state changes nearly every day, but the responsibility of courts to assure integrity in the selection of jurors does not,” he wrote.

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“The obligation to avoid discrimination in jury selection is a pivotal one,” Cuéllar wrote. “It is the duty of courts and counsel to ensure the record is both accurate and adequately developed.”