The death penalty in the United States has a race problem. African Americans are vastly overrepresented on death row: 42 percent of death row inmates are African American, which is more than three times higher than their share of the US population. But it's not the racial disparities in the outcome that are most illustrative of the death penalty's race problem. It's the racial disparities throughout the entire process: African Americans are simultaneously the people most affected by death-penalty cases, and the people least likely to have a say in them.

In 2009, North Carolina passed the Racial Justice Act to uncover some of these racial discrepancies — and allow death-row inmates to have their cases reconsidered if they found enough evidence that their initial trial was racially skewed. The law was repealed in 2013, and the only inmates who got off death row under the law are in danger of having their death sentences reinstated. But as a result of the legislation, researchers and the public now know more about the racial dynamics behind jury selection in death-penalty cases.

Here's how the death penalty sets up a vicious cycle when it comes to race.

1) Racial disparities in outcomes reinforce racial disparities in public opinion

A slim majority of Americans — 55 percent — support the death penalty. But its political support comes from the group that's least likely to be sentenced to death. Sixty-three percent of whites support the death penalty, as opposed to 36 percent of African Americans (and 40 percent of Hispanics).

What's more, calling attention to the racial disparities might not make whites more wary of supporting the death penalty — in fact, it might make them more enthusiastic. One 2007 study looked at whether poll respondents were less likely to support the death penalty after hearing various arguments against it. It found that whites "actually become more supportive of the death penalty upon learning that it discriminates against blacks." (This is similar to other studies, which have shown white people are more likely to support harsh prison policies if they believe that black people are overrepresented in prisons.)

2) Racial disparities in public opinion affect who's allowed to get seated on juries

you can't get seated on a jury in a death-penalty case if you oppose the death penalty

You can't get seated on a jury in a death-penalty case if you oppose the death penalty. Jurors have to be willing to consider every option in sentencing — and in cases where the death penalty is an option, that means they have to be willing to consider sending the defendant to death row. If a juror isn't "death qualified" because he or she opposes the death penalty, he or she automatically gets bounced from the jury pool.

As the Virginia Quarterly Review wrote in 2014, this means that a lot of potential black jurors get disqualified:

Death qualification is one reason behind racial disparities on juries. More than three decades of research have shown that capital juries tend to be less representative of the general population because women and African Americans are more likely to disapprove of the death penalty than white men. In the early 1980s, University of California, Berkeley, sociologist Robert Fitzgerald and Stanford (now University of Michigan) psychologist Phoebe Ellsworth found that, among 811 eligible jurors in Alameda County, California, about 25 percent of blacks were automatically excluded from capital-jury pools because of their disapproval, compared to 15 percent of whites.

3) No matter what they believe, blacks are much less likely to get seated on juries in death-penalty cases

When picking a jury, prosecutors and defense attorneys each get a certain number of peremptory challenges: free passes to veto people from serving on the jury, without having to give a reason why. This is only after jurors have been "death qualified," which means the prosecutor has an advantage: If a potential juror seems overly enthusiastic about the death penalty, the defense attorney will have to spend a challenge to strike him, but a potential juror who is anti-death penalty will be bounced before he even gets in front of the lawyers.

Even black would-be jurors who do support the death penalty often end up getting bounced by prosecutors. When North Carolina passed its Racial Justice Act, researchers were asked to conduct a review of the racial compositions of the juries that had sent North Carolina's death-row inmates to die — and who'd been left off those juries. Here's what they found (per the Virginia Quarterly Review):

Over the twenty-year period, prosecutors were more than twice as likely to strike qualified candidates who were black, and that the disparity persisted "statewide, by judicial division, by prosecutorial district." ...The factors often used to explain the dismissal of black (potential jurors) — reservations about the death penalty, economic hardships, past run-ins with the law — had no significant effect on the strike-rate disparity. That is: When these factors were accounted for and held constant, a black potential juror was still more than twice as likely to be struck. The researchers also found that more than 40 percent of the inmates on death row had been sentenced by juries that were either all-white or included only one person of color.

"prosecutors were more than twice as likely to strike qualified candidates who were black"

Of course, it's illegal to strike a potential juror just because of race. That's the result of a Supreme Court case from 1986 called Batson v. Kentucky. But when North Carolina started reconsidering the cases of some death-row inmates under its now-repealed law, attorneys for the inmates found out how prosecutors were trained to get around this:

A "cheat sheet" (was) acquired from one of the trainings overseen by the NCCDA. Formally titled "BATSON Justifications: Articulating Juror Negatives," the document lists nine specific race-neutral explanations—such as appearance, attitude, dress, and body language—and a tenth catchall—"any other sign of a defiance, sympathy with the defendant or antagonism to the State"—that "courts have approved as neutral explanations," according to Duke University law professor James Coleman.

The training document didn't instruct prosecutors to strike jurors based on race and then pretend there was another reason. But if prosecutors wanted to do that, the document showed them how to get away with it.

And prosecutors who'd been trained in "articulating" nonracial objections would be able to strike jurors just based on gut feelings. They'd only have to give a reason at all if the defense attorney issued a "Batson challenge" alleging that the decision was race-based, and then prosecutors would be able to use one of the judicially approved "race-neutral explanations."

4) Black defendants are much more likely to get the death penalty — especially from nonblack juries

So black defendant in a death-penalty case is unlikely to be tried by a jury of his racial peers. And the absence of African Americans on death-penalty juries is one big reason why African Americans are so overrepresented on death row.

One study (as reported by VQR) found that black defendants were more likely to get sentenced to death, no matter who was on their jury. But while diverse juries were more likely to send black defendants to death than white defendants, all-white juries with black defendants had the highest death-sentence rate of all:

In Philadelphia, juries, no matter their racial composition, sentenced black defendants to die at higher rates than nonblack defendants. Moreover, predominately non-black juries were significantly more punitive toward black defendants than were black-majority juries. In other words, the racial makeup of the jury and of the defendant heavily influenced the sentencing outcome.

Another study the VQR highlights focused on whether a jury found someone guilty, not whether they sentenced him to death. That study showed that black defendants weren't disproportionately likely to get convicted, as long as their juries were diverse:

between 2000 and 2010 all-white juries in Florida were 16 percent more likely to convict black defendants than white defendants, and that the conviction gap was "nearly eliminated" when the jury pool included at least one black member.

It's possible that both are true. A diverse jury might not be any more likely to find black defendants guilty than white ones, but once they're convicted, the jury might still be more likely to sentence black defendants to death.

Research conducted by psychologist Jennifer Eberhardt, who won a 2014 Macarthur Fellowship for her work on race and the criminal justice system, shows how the deeply rooted "implicit bias" association of blackness with criminality affects death penalty cases. One study she conducted looked at the facial features of death penalty defendants, and found that "the more stereotypically black a person's physical features are perceived to be, the more that person is perceived as a criminal.… Even in death penalty cases, the perceived blackness of a defendant is related to sentencing: the more black, the more deathworthy."

So both in theory and in the context of a specific case, there's evidence that white support for the death penalty is partly due to implicit bias against black defendants. In the jury room, it's possible that black jurors could be a check on the implicit bias of white ones. But African Americans are disproportionately excluded from the jury room.

5) Statistics are the only way to show these phenomena are widespread, but it's impossible to use statistics to challenge an individual ruling or case

The problem that North Carolina ran into in implementing its Racial Justice Act is that once the state collected statistics about jury selection, it had to figure out how those statistics related to individual cases. And as one opponent of the law said, the Constitution strictly requires judges to look at each case on the merits. That makes it very hard to set rules for an individual case based on a general phenomenon. From the VQR:

"The problem is, constitutionally, we can't use statistics when picking a jury," said Silver, one of the few black prosecutors in the state. "You're evaluating the jurors on the statistics. So in a very real sense the only way to remedy that is to have proper statistics. But to remedy by proper statistics is per se unconstitutional. Thus there is no way to comply with the statute."

This sort of thing is generally an obstacle that policymakers run into when they're trying to fix problems of systemic bias. Juries in death penalty cases aren't racially skewed because prosecutors are individually, deliberately racist — or if they are, as the training document shows, they've learned how to cover their tracks. The death penalty's race problem is that a bunch of overlapping phenomena, which look neutral in any particular case, add up to a general disparity in who's represented on juries and who's sentenced to death. It's only possible to see that disparity once you zoom out to the level of statistics or aggregate research. But those statistics don't say much about what to do in an individual case — where, again, bias isn't immediately apparent.

a bunch of overlapping phenomena, which look neutral in any one case, add up to a general disparity in who's on juries and who's sentenced to die

North Carolina's law was eventually watered down. Under the rewritten law, any defendant who wanted to get on death row would have to prove racism had been a factor in his particular trial. Then, even the watered-down version got repealed once Republicans took over the state legislature in 2013.

But even if North Carolina's law didn't turn out to be the solution to the death penalty's race problem, it's the reason that we know the problem exists. The data it uncovered can't be repealed.