TIMOTHY TYRONE FOSTER, a black man, sits on Georgia’s death row for killing an elderly white woman in 1986. When jurors were being vetted to hear Mr Foster’s case, prosecutors struck all five African Americans from the jury pool. Four of those strikes came via “peremptory challenges”, tools by which lawyers can nix potential jurors without having to cite a reason. In his closing argument, the prosecutor told the all-white jury that sentencing Mr Foster to die would “deter other people out there in the projects”—public housing blocks populated mainly by African-Americans. Overt racism in jury selection has been illegal in America since the Strauder v West Virginia ruling in 1880. But lawyers continue to strike blacks from juries at suspiciously high rates, as an amicus brief in Foster v Chatman—a case the Supreme Court heard on November 2nd—details. In North Carolina, a state court found in 2012 that in 173 capital cases, 52.8% of potential black jurors were cut, compared to 25.7% of non-black individuals. A few years earlier in Louisiana, a court found that blacks were three times more likely than whites to be roped out of the jury box. In Houston County, Alabama, where 27% of the residents are black, half of death-penalty juries wound up all-white from 2005 to 2009; the rest had only one African-American juror.

Mr Foster’s trial took place in the aftermath of the Supreme Court’s 1986 ruling in Batson v Kentucky. Batson held that racial considerations are out of bounds in jury selection. When issuing peremptory challenges, the court said, lawyers must be ready to present a race-neutral explanation for their strikes. Justice Thurgood Marshall voted with the majority in Batson, but he warned Americans not to expect too much from the ruling. "The decision today will not end the racial discrimination that peremptories inject into the jury-selection process,” he wrote. “That goal can be accomplished only by eliminating peremptory challenges entirely."

Justice Marshall’s caveat seems prescient today. As the amicus brief by former prosecutors explains, discriminatory motives during voir dire, as the jury selection process is called, are often “veiled by purportedly ‘race-neutral’ justifications prepared by prosecutors for the very purpose of defending their race-motivated strikes”. Among the pretexts for discrimination are the potential juror’s “low intelligence”, eyeglasses, marital status, age, address in a “bad part of town”, suspicious gait or propensity—no joke—to chew gum. In the case of Mr Foster, prosecutors presented a long list of supposed reasons for striking the African-Americans from the jury: they were too young to identify with the elderly victim, appeared bored, had relatives who were social workers or did not make sufficient eye contact. The judge bought these explanations, apparently without winking, and Mr Foster was sentenced to die.

But 20 years later, serious doubt was cast on the prosecution’s motives when Mr Foster got his hands on the notes prosecutors kept during voir dire. The details are shocking: the lawyer had marked each black juror with a “B” and highlighted their names in green ink. He numbered them (“B#1”, “B#2”, and so on), and—most damningly—compared them and discussed which is the lesser of the evils if “it comes down to having to pick one of the black jurors”. As Steven Bright, Mr Foster’s lawyer, told the justices on Monday, this evidence amounts to “an arsenal of smoking guns”. It is, in the estimation of Justice Elena Kagan, “as clear a Batson violation as a court is ever going to see”.

The unenviable job of defending the prosecutors’ conduct fell to Beth Burton, a deputy attorney general from Georgia. She argued that the notes “certainly can be interpreted in two ways.” The reading on offer from Ms Burton painted a portrait of prosecutorial innocence. Since Batson had just been decided the year before, it was very much on the minds of the prosecutors. They could anticipate that challenges would arise to their peremptory strikes and it made sense to keep careful track of the black members of the jury pool so they would be prepared to offer race-neutral explanations of the strikes.

Justice Stephen Breyer had fun taking apart this line of argument. The reason for highlighting the black jurors’ names “was because he was preparing a defense in case of a Batson challenge”? Correct, Ms Burton said. But this explanation never came up until very recently. “[I]sn’t it a little surprising that he never thought of it?” Justice Breyer was also dubious of the post-hoc “race-neutral” rationalisations for the strikes. Some of those might sound valid in retrospect, but the question is which reasons actually motivated the prosecutor’s decision to strike all the blacks from the jury:

Now, if my grandson tells me, I don't want to do my homework tonight at 7:00 because I'm just so tired. And besides, I promised my friend I'd play basketball. And besides that, there's a great program on television. And besides that, you know, I really—my stomach is upset, but I want to eat spaghetti. And so he's now given me five different reasons.

A snaggle-toothed procedural tangle that unexpectedly occupied the court for about half of the hearing on Monday may result in the case returning to a Georgia state court for another hearing. But if the justices decide Foster on the merits, it seems likely the prosecutors will get a good scolding. It’s unclear, though, if a win for Mr Foster will be a signal to prosecutors to clean up their acts—or simply to keep less incriminating notes.