Read: The Supreme Court confronts racism in the jury room

The next two trials ended in mistrials because the jurors could not agree. The second time that happened, the trial judge had the lone holdout—an African American juror—arrested in the courtroom, and threatened to jail Flowers’s African American lawyer. Charges against the juror were dropped, but a message was sent. The sixth time, in 2010, a jury agreed that Flowers was guilty of four murders and sentenced him to death.

Formally, that sixth conviction is the only one before the Supreme Court. Again, the issue is whether Evans deliberately used race to exclude eligible members of the jury pool. Answering that question requires understanding the rules of jury selection.

A prosecutor or defense lawyer may conclude after questioning that a specific juror is likely to vote for the other side. If there’s a good reason to think the juror can’t be fair—if, for example, a juror is closely related to a party or witness, or if a juror expresses the belief that the police usually lie (or usually tell the truth)—a lawyer can have the juror excluded “for cause.” But that leaves a lot of jurors who may give off a worrisome vibe to one side or the other. To address this concern, each side is given a fixed number of “peremptory challenges,” or strikes; when counsel uses one, a potential juror is automatically excused. If the process goes on long enough, eventually both sides run out of challenges.

Although the peremptory-challenge system is a venerable part of American criminal procedure, it can conflict with a more important principle: that deliberate use of race to exclude jurors violates the constitutional guarantee of “the equal protection of the laws.”

The 1986 Supreme Court case Batson v. Kentucky tried to forestall race-related misconduct; Batson and related cases established procedures for rooting out improper exclusions. In brief: If challenges by a prosecutor (or, less often, a defense lawyer) seem to follow a racial pattern, opposing counsel may allege a “prima facie” case of discrimination; if the judge agrees that there is a questionable pattern, he or she convenes a “Batson hearing,” in which the lawyer using the challenges is allowed to give a “non-racial” reason for each challenge. The objecting party has the burden of proving that the excuses are bogus; if it does, the trial judge may order the excluded juror(s) seated; the judge may also dismiss the entire jury panel and begin jury selection with a new pool. If the “non-racial” reasons convince the trial judge, however, the Batson motion will be rejected, and the case will proceed to trial. If, after a conviction, an appeals court finds a Batson violation, the remedy is a new trial.

Read: Should racism in the jury room lead to a new trial?

In Flowers’s most recent trial, his lawyer pointed out to the judge that Evans devoted much more time to questioning black potential jurors than whites—as if perhaps searching for some reason to exclude them. In the Batson hearing, Evans cited some reasons that didn’t seem justified by the facts, or might have applied to white jurors if he had asked. The defense asked the trial judge to consider the two previous trials in which Evans was found by higher courts to be misusing peremptory strikes. But the trial judge accepted Evans’s rulings as “race-neutral,” and overruled the Batson motion because the defense couldn’t show him white jurors who had been accepted despite presenting the identical reason for removal. The jury that resulted had 11 white members and one African American; it convicted Flowers and sentenced him to death. The state appeals courts this time found no fault with the verdict.