You probably assumed that a unanimous jury was required for a criminal conviction, but the truth is that two states had allowed non-unanimous juries in criminal cases. Louisiana and Oregon were the hold-out states, and Louisiana changed its constitution to require unanimous juries in 2018. However, people who were convicted by non-unanimous juries did not get the benefit of the change, as the amendment was not made retroactive.

That left untold numbers of people sitting in prison when the jury that convicted them was not unanimous. That included Evangelisto Ramos, who had been convicted, on a vote of 10-2, of murdering a woman in 2014. He was sentenced to life in prison without parole. Ramos has always maintained his innocence in the case.

His case recently made it to the U.S. Supreme Court, which overturned a thin precedent to rule that unanimous juries are required by the U.S. Constitution in criminal cases. The decision, written for the majority by Justice Neil Gorsuch, found that jury unanimity is such a fundamental matter of fairness that it is required by the Due Process clause.

In reaching their decision, the justices looked at the history of unanimous and non-unanimous juries, including the allegation that allowing non-unanimous juries was a step taken in an effort to suppress minorities. The justices found substantial historical evidence that this was true.

“While we applaud this decision, it is an embarrassment on our system that it was not held until 2020,” said a commentator with the group Conservatives Concerned About the Death Penalty. “There remain in prisons, and even on death rows, those who were convicted by non-unanimous juries that we hope the courts will hasten to reckon with as well.”

This ruling could mean that all those convicted by non-unanimous juries will have to be released. Lawyers for those affected will need to bring petitions arguing that their clients’ due process rights were violated by their non-unanimous convictions.