Police officers stand by outside the White House as black religious leaders from Chicago demonstrate against the murder of 14-year-old Emmett Till on Oct. 24, 1955. (Anonymous/Associated Press)

When Bill Baxley assumed office as Alabama attorney general in 1971, he was determined to bring to justice the bombers who lit the dynamite beneath the 16th Street Baptist Church in Birmingham, killing four little black girls Sept. 15, 1963.

A state jury had refused to convict one of the men, Robert Chambliss, on murder charges.

But in 1976, Baxley reopened the case and eventually got a murder conviction for Chambliss, who died in prison. Many across the South believed that with the guilty verdict, Southern juries — once defiantly loath to convict whites for the murder of blacks — had begun a judicial trek toward fairness.

With the acquittal this weekend of George Zimmerman, who fatally shot 17-year-old Trayvon Martin, those feelings, especially among many blacks, were upended. A jury of six women — five whites and one described as a white Hispanic — found the neighborhood watch volunteer, who said he shot the unarmed Martin in self-defense, not guilty of second-degree murder and manslaughter. The jury deliberated more than 16 hours after a three-week trial in Sanford, Fla.

A Southern jury — when it comes to race and the perception that a black person has been wrongly accused or harmed — operates under the wide, whispering shadow of history. And there exists a roster of names and cases that has exploded onto the national scene and claimed headlines against this backdrop of race and geography: the Scottsboro Boys, Emmett Till, Isaac Woodward, Medgar Evers, the four girls killed in the Alabama bombing.

After the Zimmerman verdict, civil rights activists have clamored for charges of federal civil rights violations. President Obama referred to Martin’s death as “a tragedy.” On Monday, Attorney General Eric H. Holder Jr. called the teenager’s death “unnecessary” and said the Justice Department would continue its investigation of the shooting.

The case, fairly or not, has reignited passions about the South and Southern juries when it comes to justice for blacks. It is a story line so often mentioned that it is now wedded to popular culture, in literature — the works of Eudora Welty, William Faulkner and Ralph Ellison — as well as in movies. In “To Kill a Mockingbird,” a black man wrongly accused of raping a white woman is convicted despite the defense waged by his heroic white attorney. FBI agents in “Mississippi Burning” seek justice for three voting- rights activists.

Baxley began working as a lawyer in Alabama at the height of the civil rights movement, when blacks were routinely tossed in jail for protesting. “When I started practicing,” Baxley says, “there were no women on juries. And very few blacks, if any.”

Baxley acknowledges, in light of the Zimmerman verdict, that Southern juries may have to constantly fight to overcome history and the perception that they cannot mete out justice when it comes to blacks who have been wronged. “It requires evolution,” he says of certain juries. “And evolution is slow. There are ingrained attitudes, and some of those are based on fear.”

Baxley, who is white, believes that the South has made appreciable advances when it comes to courtroom justice and must be viewed in terms of history. “It’s a vast difference from what it used to be,” he says. “I remember the 1960s in Alabama. Sometimes you would have a confession by whites who had done violence against blacks. And the jury would still come back with acquittals! Sometimes the police would do a great job, but the jury would turn them loose.”

He says he understands the strong emotions in the Martin case but argues that the prosecution had a high hurdle. “I think this case would have been hard to win in any state,” he says. “I think it was just difficult for the prosecution. You did have a guy [Zimmerman] with some kind of injuries.”

The fact that there were still culprits loose in the Birmingham church bombing after Chambliss had been sent to prison was not lost on Doug Jones, who as a U.S. attorney in Alabama, brought and won convictions against two others, Tommy Blanton in 2001 and Bobby Frank Cherry in 2002.

Jones, who is white, says that he believes there is a racial dynamic to the Martin killing but that the jury was in a difficult position. “I believe Zimmerman racially profiled Martin,” he says. “We know there was an altercation. So I think there are intervening factors here that the jury had to look at.”

Zimmerman’s mother is Peruvian, and his father is white.

Clifford Alexander, who is black, was a young lawyer when he worked in the White House under President Lyndon B. Johnson. He well remembers discussions about judges and juries in Southern courtrooms in those days. And he understands why conversations reverted to such reflections in the aftermath of the Zimmerman verdict. “The clear reason why Zimmerman had the audacity to approach this child was that he saw the color of his skin as a threat,” he says.

He says it was particularly galling that after Martin was killed, there was no immediate arrest, which only hardened sentiments about Southern law enforcement. “We all know Zimmerman wasn’t arrested until later. And you had a dead young man right there!” he says.

Alexander, who went on to head the Equal Employment Opportunity Commission, said the Zimmerman verdict and other actions by law enforcement, such as New York City’s stop-and-frisk policy, leave blacks with impressions of unfair treatment.

“Jurors in the past often were not treating black life like they would a white life. There are still, today, too many differentials in treatment,” he said. “We have been, as a society — and often as a government — unable to describe the racism of certain things.”

It was Welty, a white writer from the South, who sought in 1963 to describe racism in a short story, “Where Is the Voice Coming From?” Revered as one of this country’s most gifted writers, she did not regularly write about race and crime in her native South. But Evers’s killing so affected her that she sat down at her typewriter and, according to legend, wrote the five-page story in one day. Her story was a fictionalized portrait of the night Evers was murdered in the driveway of his Jackson, Miss., home. The narrator is the gunman. “Something darker than him, like the wings of a bird, spread on his back and pulled him down. He climbed up once, like a man under bad claws, and like just blood could weigh a ton he walked with it on his back to better light. Didn’t get no further than his door. And fell to stay.”

Evers’s real-life killer, Byron De La Beckwith, was tried twice in 1964, each time resulting in hung juries. Thirty years later, in 1994, after new evidence was uncovered, a jury of eight blacks and four whites found him guilty of first-degree murder.