The US federal government has reopened its investigation into the death of Emmett Till, the black teenager whose brutal killing shocked the world and helped inspire the civil rights movement.

The Justice Department told Congress in a report in March that it is reinvestigating Emmett’s killing in Money, Mississippi, in 1955 after receiving “new information”.

The case was closed in 2007, with authorities saying the suspects were dead; a state grand jury did not file any new charges.

The federal report, sent annually to politicians under a law that bears Emmett’s name, does not indicate what the new information might be.

But it was issued in late March following the publication last year of The Blood Of Emmett Till, a book that says a key figure in the case acknowledged lying about events preceding the killing of the 14-year-old youth from Chicago.

The book, by Timothy B Tyson, quotes a white woman, Carolyn Donham, as acknowledging during a 2008 interview that she was not truthful when she gave evidence that Emmett grabbed her, whistled and made sexual advances at a store in 1955.

Carolyn Bryant
Carolyn Bryant, later Donham (Gene Herrick/AP)

Two white men – Ms Donham’s then-husband Roy Bryant and his half-brother JW Milam – were charged with murder but acquitted over the killing of Emmett, who had been staying with relatives in northern Mississippi at the time.

The men later confessed to the crime in a magazine interview, but were not retried.

Both are now dead.

Ms Donham, who turns 84 this month, lives in Raleigh, North Carolina.

A man who came to the door at her residence declined to comment about the FBI reopening the investigation.

Paula Johnson, co-director of an academic group that reviews unsolved civil rights killings, said she cannot think of anything other than Tyson’s book that could have prompted the Justice Department to reopen the investigation.

“We’re happy to have that be the case so that ultimately or finally someone can be held responsible for his murder,” said Ms Johnson, who leads the Cold Case Justice Initiative at Syracuse University.

Deborah Watts, Emmett’s cousin and co-founder of the Emmett Till Legacy Foundation, said it is “wonderful” that the killing is getting another look but did not want to discuss details.

She said: “None of us wants to do anything that jeopardises any investigation or impedes, but we are also very interested in justice being done.”

Abducted from the home where he was staying, Emmett was beaten and shot, and his mutilated body was found weighted down with a cotton gin fan in the Tallahatchie River.

Images of his mutilated body in a coffin gave witness to the depth of racial hatred in the Deep South and helped build momentum for subsequent civil rights campaigns.

Relatives of Emmett pushed attorney general Jeff Sessions to reopen the case last year following publication of the book.

Ms Donham, then known as Carolyn Bryant and 21 years old at the time, gave evidence in 1955 as a prospective defence witness in the trial of Bryant and Milam.

JW Milam, left, his wife, Roy Bryant, far right, and his wife Carolyn Bryant in a courtroom in Sumner, Mississippi
JW Milam, left, his wife, Roy Bryant, far right, and his wife Carolyn Bryant in a courtroom in Sumner, Mississippi (AP)

With jurors out of the courtroom, she said a “n***** man” she did not know took her by the arm.

“Just what did he say when he grabbed your hand?” defence lawyer Sidney Carlton asked, according to a trial transcript released by the FBI a decade ago.

“He said, ‘How about a date, baby?'” she said.

Ms Bryant said she pulled away, and moments later the young man “caught me at the cash register”, grasping her around the waist with both hands and pulling her towards him.

“He said, ‘What’s the matter baby, can’t you take it?'” she said.

Ms Bryant also said he told her “you don’t need to be afraid of me”, claiming that he used an obscenity and mentioned something he had done “with white women before”.

A judge ruled the evidence inadmissible.

An all-white jury freed her husband and the other man even without it.

Evidence indicated a woman might have been in a car with Bryant and Milam when they abducted Emmett, but no-one else was ever charged.

In the book, Tyson wrote that Ms Donham told him her evidence about Emmett accosting her was not true.

“Nothing that boy did could ever justify what happened to him,” the book quotes her as saying.