Here are some reasons prosecutors have offered for excluding blacks from juries: They were young or old, single or divorced, religious or not, failed to make eye contact, lived in a poor part of town, had served in the military, had a hyphenated last name, displayed bad posture, were sullen, disrespectful or talkative, had long hair, wore a beard.
The prosecutors had all used peremptory challenges, which generally allow lawyers to dismiss potential jurors without offering an explanation. But the Supreme Court makes an exception: If lawyers are accused of racial discrimination in picking jurors, they must offer a neutral justification.
“Stupid reasons are O.K.,” said Shari S. Diamond, an expert on juries at Northwestern University School of Law. Ones offered in bad faith are not.
In Louisiana’s Caddo Parish, where Shreveport is the parish seat, a study to be released Monday has found that prosecutors used peremptory challenges three times as often to strike black potential jurors as others during the last decade.
That is consistent with patterns researchers found earlier in Alabama, Louisiana and North Carolina, where prosecutors struck black jurors at double or triple the rates of others.
In Georgia, prosecutors excluded every black prospective juror in a death penalty case against a black defendant, which the Supreme Court has agreed to review this fall.
“If you repeatedly see all-white juries convict African-Americans, what does that do to public confidence in the criminal justice system?” asked Elisabeth A. Semel, the director of the death penalty clinic at the law school at the University of California, Berkeley.
As police shootings of unarmed black men across the country have spurred distrust of law enforcement by many African-Americans, the new findings on jury selection bring fresh attention to a question that has long haunted the American justice system: Are criminal juries warped by racism and bias?
Some legal experts said they hoped the Supreme Court would use the Georgia case to tighten the standards for peremptory challenges, which have existed for centuries and were, until a 1986 decision, Batson v. Kentucky, considered completely discretionary. (Judges can also dismiss potential jurors for cause, but that requires a determination that they are unfit to serve.)
But many prosecutors and defense lawyers said peremptory strikes allow them to use instinct and strategy to shape unbiased and receptive juries. “I’m looking for people who will be open, at least, to my arguments,” said Joshua Marquis, the district attorney in Astoria, Ore.
Jeff Adachi, San Francisco’s elected public defender, said peremptory challenges promote fairness.
“You’re going to remove people who are biased against your client,” he said, “and the district attorney is going to remove jurors who are biased against police officers or the government.”
Reprieve Australia, a group that opposes the death penalty and conducted the Caddo Parish study, said the likelihood of an acquittal rose with the number of blacks on the jury.
Excluding black jurors at a disproportionate rate does more than hurt defendants’ prospects and undermine public confidence, said Ursula Noye, a researcher who compiled the data for the report.
“Next to voting,” she said, “participating in a jury is perhaps the most important civil right.”
‘It Dashes Your Hopes’
Prospective jurors arriving at the courthouse here walk past a towering monument to the Confederacy, featuring grim likenesses of four Confederate generals.
Carl Staples, a 63-year-old African-American, recalled how the monument made him feel when he reported for jury duty.
“It dashes your hopes,” he said, taking a break at the gospel radio station where he works as an announcer. “It has its roots in the ideology of white supremacy.” He said much the same thing during jury selection in a 2009 death penalty case, and that played a part in his dismissal for cause.
Caddo Parish is 48 percent black, and 83 percent of the defendants in the new study were black. But the typical 12-member criminal jury had fewer than four blacks on it, the report said.
Much of the gap had nothing to do with peremptory strikes. Of the 8,318 potential jurors in the study, which reviewed 332 trials from 2003 to 2012, only 35 percent were black.
Professor Diamond suggested reasons for this. Blacks may be less likely to be on jury lists that are drawn from voter registration records, less likely to appear when called, more likely to qualify for hardship exemptions and more likely to be disqualified for felony convictions.
Still, prosecutors here used peremptory strikes against 46 percent of the black potential jurors who remained, and against 15 percent of others. In 93 percent of trials, prosecutors struck a higher percentage of blacks than of others.
Dale Cox, the parish’s acting district attorney, said jury selection was more art than science and could not be quantified. “Statistics can be misleading,” he said. “There could be any number of variables that would explain those strikes that have nothing whatsoever to do with race.”
The study’s findings, though, were in keeping with data from around the country.
In a five-year period ending in 2010, according to a lawsuit, prosecutors in Houston and Henry Counties in Alabama used peremptory strikes to remove 82 percent of eligible black potential jurors from trials in which the death penalty was imposed.
There can be good reasons for that, said Kent S. Scheidegger, a lawyer with the Criminal Justice Legal Foundation, which generally supports prosecutors.
“Opposition to the death penalty is much more common among black people, polls regularly show,” he said. Striking jurors for hesitation about capital punishment is legitimate, he continued, adding that it is largely balanced ”by defense lawyers doing exactly the same thing the other way.”
The judge, Gregory A. Weeks of Cumberland County Superior Court in Fayetteville, endorsed a study by law professors at Michigan State University examining the trials of the state’s death row inmates in 2010. It found that prosecutors had struck 53 percent of black potential jurors and 26 percent of others.
In Caddo Parish, the new study said, Mr. Cox struck black jurors at 2.7 times the rate of others over the course of 22 trials. (Mr. Cox recently expressed unusual enthusiasm for the death penalty.)
He denied any improper conduct, and noted that he had never had a conviction questioned by a court or reversed because of his jury selection practices.
He added that it was not always clear whether black jurors helped or hurt the prosecution.
“The defendant on trial may be African-American and the victim is African-American,” he said. “That is a scenario that is 90 percent of our cases here in Shreveport. So you can see right away I want African-Americans on the jury, by and large, because they are the voice of the victim.”
Of the 12 prosecutors who handled at least 20 trials, 10 were white. The highest dismissal rate was held by Brian H. Barber, a white former prosecutor who struck five times as many blacks as others. Now a judge, he did not respond to requests for comment.
Circling the Word ‘Black’
When the Supreme Court hears the death-penalty case from Georgia, Foster v. Chatman, No. 14-8349, it could reshape the ways juries are selected.
The case arose from the 1987 trial of Timothy T. Foster, an African-American facing the death penalty for killing a white woman, Queen Madge White. Prosecutors worked hard to exclude blacks from the jury.
In notes that did not surface until decades later, they marked the names of black prospective jurors with a B. They highlighted those names in green. They circled the word “black” where potential jurors had noted their race on questionnaires.
They ranked the black prospective jurors in case “it comes down to having to pick one of the black jurors,” as the prosecution’s investigator put it in a draft affidavit at the time.
There was no need for that, though. Prosecutors struck all four black potential jurors.
When challenged, Stephen Lanier, the lead prosecutor, offered lots of reasons for the strikes. All the prospects were said to be some combination of confused, incoherent, hostile, disrespectful and nervous. Three did not make enough eye contact. A 34-year-old black woman was too close in age to the defendant, who was 19. (The prosecution did not challenge eight prospective white jurors age 35 or under.)
“All I have to do is have a race-neutral reason,” Mr. Lanier said, “and all of these reasons that I have given the court are racially neutral.” The judge rejected the defense’s objection.