“I think if I would have won, maybe it wouldn’t have made a change to everyone in the country, maybe just in Colorado,” he said. “Now that it’s at the Supreme Court, I think it’s got a chance to make a difference for other people.”

In earlier cases, the United States Supreme Court has said that even egregious misconduct in the jury room cannot be used to challenge a conviction if it would require jurors to testify about what was said there. But the court has never squarely confronted whether racial or ethnic prejudice requires an exception to the general rule.

In 1987, in Tanner v. United States, the Supreme Court let stand convictions in a mail fraud case in Florida even though the jury had treated the trial as “one big party” fueled by “rampant drug and alcohol abuse,” as one juror described it. During recesses, jurors drank pitchers of beer and liters of wine, and they used marijuana and cocaine.

Afterward, in the courtroom, some jurors slept. One was “in a sort of giggly mood.”

Justice Sandra Day O’Connor, writing for the majority, said there were good reasons to ignore “irresponsible or improper juror behavior” if it was based on jurors’ accounts of what had gone on in the jury room.

After-the-fact challenges based on jurors’ testimony, she wrote, would make it less likely that jurors would speak candidly during deliberations. Allowing such challenges would encourage lawyers to harass former jurors, she said, and undermine the finality of verdicts.

In 2014, in Warger v. Shauers, the Supreme Court unanimously ruled that jurors may not testify about what went on during deliberations, even to expose dishonesty during jury selection.