On November 3 1979 five Communist Worker party members were killed and 10 other people wounded at a demonstration against the Ku Klux Klan in Greensboro. Four television stations caught Klan and American Nazi party members removing guns from the boots of their cars but two trials, with all-white juries, ended in acquittals.

Now a body, modelled on post-apartheid South Africa's Truth and Reconciliation Commission, plans to examine the events, through public testimony and documentation in order to reckon with the town's past.

"A significant portion of the Greensboro community do not feel that what's done is done," says Lisa Magarrell, of the International Centre for Transitional Justice, which is the principal adviser to the commission. "Some of the issues that were raised then remain even today. It's not driven by a desire for retribution but to bring people together."

But unlike the South African model, the process neither bears the imprimatur of the authorities nor offers amnesty in return for the full testimony of the perpetrators.

"It's going to have to rely on its moral credibility to get people to cooperate with it," says Paul van Zyl, who served as the executive secretary of South Africa's TRC and has general responsibility for the ICTJ's work. "It can't just be a body which is seen as dealing with black people's grievances. Despite their best intentions that is a risk but it is one they are alive to in Greensboro and have made steps to try and avoid."

But while some believe the process is vital to heal the community, others believe it will simply reopen old wounds.

"I don't believe this event is on the lips and the minds of most of us," Mayor Keith Holliday told the Charlotte Observer last year when the process started. "Everybody felt horrible when it happened, but we've put it behind us."

Greensboro, which also witnessed the most prominent lunch-counter sit-in in 1960 when four black students ordered food from a "whites-only" diner, is just one town among many in the south struggling to come to terms with the ugly side of its history, as some seek closure and justice, arguing that it is the only way to understand the present and move on.

Last month the United States justice department reopened the case of Emmett Till, the black teenager who was murdered in Mississippi in 1955, after documentary makers unearthed new witnesses who had not testified at the original trial.

Fourteen-year-old Emmett, from Chicago, was abducted from his uncle's home in the southern hamlet of Money in August 1955, after accusations that he had wolf-whistled at a white woman, Carolyn Bryant.

His body was pulled from the Tallahatchie river with a bullet in the skull, an eye gouged out and his forehead crushed on one side. The two white men accused of killing him were acquitted by an all-white jury but one later confessed to a magazine.

"As a nation, we should never be afraid to acknowledge our mistakes - however difficult - so that we can learn from them," argued a senator, Charles Schumer, who lobbied for the case to be reopened.

"The truth, as they say, will set you free. It's no less true in the case of Emmett Till from 50 years ago than it is today."

Meanwhile in Philadelphia, Mississippi, the small town where the murder of three young civil rights workers in 1964 provided the basis for the film Mississippi Burning, efforts to erect a memorial in their honour have energised some and enervated others.

Last week a 20-stop bus tour remembering those who died that year made its way from New York to the south.

"This is not a dead-end issue," said Ben Chaney, whose brother James was murdered in Mississippi. "There is no statute of limitation on murder."

Seven members of the Ku Klux Klan were convicted of federal civil rights violations in the murders and sentenced to prison terms ranging from three to 10 years. The state never brought murder charges, and none of those convicted served more than six years.

Urging black people to register to vote and then to cast their ballots was the best way to get his brother's case reopened, Mr Chaney said, explaining: "It puts pressure on the prosecutor to prosecute."

"People keep saying if you leave it, it will go away," says Leroy Clemons, the leader of the Philadelphia chapter of the National Association for the Advancement of Coloured People (NAACP), which, along with the editor of the local newspaper, is calling for the case to be reopened. "But it's not going to go away. If anyone should tell this story then it should be us. It's our story."

James Prince, the white editor of the local newspaper, the Neshoba Democrat, who along with Mr Clemons is leading the campaign for a memorial, is optimistic but says there are some people who will never agree.

"Some of them will come around and some of them won't," he says. "Some of them will die hard-hearted. It's still a struggle, not just here but everywhere. But it's a struggle we're probably better equipped to deal with precisely because of what happened here."

The divide today is not just racial but generational.

"When I was growing up no one here talked about it all, black or white," says Mr Clemons, who was two when James Chaney, Michael Schwerner, and Andrew Goodman were murdered while trying to register black voters during the Mississippi freedom summer of 1964.

"It was like it never happened. But the younger generation said, 'Let's deal with this thing and get some closure.'"

There have been some successes at bringing perpetrators to justice. In 2002 Bobby Frank Cherry was convicted of the 1963 Birmingham, Alabama, church bombing that killed four black girls. Ten years ago Byron De La Beckwith was convicted in the 1963 murder of the Mississippi NAACP leader, Medgar Evers.

But reckoning with the past also means addressing the present. Some believe that dealing with the horrors of segregation will draw a line under its legacy. "Race is not an issue now for younger people," says Mr Prince. "Today if you're willing to work hard and be honest then you're able to succeed."

Others fear these initiatives could be used to whitewash the issues that still exist as a result of discrimination.

"Some people are using the progress that has been made to wipe out any sense of the past as though they have conquered the past, but the legacy continues on death row and the continuing economic marginalisation of black people," says Charles Payne, professor of history, African-American studies and sociology at Duke University in North Carolina.

"The extent to which these initiatives can get people to think critically about how privilege is shaped is the extent to which they strike me as being real and useful."