NEW YORK -- The woman at the center of the trial of Emmett Till's alleged killers has acknowledged she falsely testified he made physical and verbal threats, according to a new book.

Historian Timothy B. Tyson told The Associated Press on Saturday that Carolyn Donham broke her long public silence in an interview with him in 2008.

His book, "The Blood of Emmett Till," comes out this week.

"She told me that, 'Nothing that boy did could ever justify what happened to him,'" said Tyson, a Duke University research scholar whose books include "Blood Done Sign My Name" and "Radio Free Dixie."

Emmett Till was a 14-year-old black child tortured and killed in 1955 in Mississippi after allegedly whistling at a white woman, then known as Carolyn Bryant.

Emmett Till's photo is seen on his grave marker in Alsip, Illinois.Chicago Sun-Times via AP

His murder became national news, was a galvanizing event in the civil-rights movement and has been the subject of books and movies.

During the trial, Bryant said he had grabbed her and, in profane terms, bragged about his history with white women.

The jury was not present when she testified.

Donham's then-husband, Roy Bryant, and his half-brother, J.W. Milam, were acquitted by the all-white jury.

Both men, who later told Look magazine they killed Till, have died.

Milam's widow, Juanita Milam, later told the FBI she believed Carolyn Bryant had fabricated her story. Juanita Milam died in 2014.

The Justice Department re-examined the case a decade ago, but no one was indicted as a murderer or an accomplice.

On Saturday, the maker of a documentary on Till said he long had been sure Bryant's story was false.

"His mother had mentioned that Emmett had a speech impediment and that the things Bryant claimed he was saying he could not have said easily," said Keith Beauchamp, whose "The Untold Story of Emmett Till" came out in 2005.

Tyson said he spoke with Donham after her daughter-in-law, Marsha Bryant, contacted him.

Bryant had read "Blood Done Sign My Name," about a racist murder during his childhood in Oxford, North Carolina, and invited Tyson to meet with her and Donham.

Tyson said he and Donham had two conversations, both lasting two to three hours, and he planned at the time to place the material in the archives at the University of North Carolina.

Asked why he waited so long to publicize his findings, he responded historians think in different terms than journalists.

"I'm more interested in what speaks to the ages than in what is the latest media thing," he said.

He said he wasn't sure whether Donham knew about the book.

He said he had fallen out of touch with the family, and when he last spoke with Bryant a few years ago, she said Donham was in poor health.

Till was a fun-loving teenager from Chicago visiting the Mississippi Delta and helping on his great-uncle Mose Wright's farm.

On Aug. 24, 1955, Till and some other children drove to a local store, Bryant's, for refreshments.

At Bryant's, some of the children stayed on the porch, watching a game of checkers, while the others filed inside to buy bubble gum and sodas.

Carolyn Bryant, the 21-year-old wife of proprietor Roy Bryant, was behind the counter.

Accounts of what happened next differ.

Mrs. Bryant claimed Emmett bragged about dating white women up north.

She said he grabbed her and asked her, "How about a date, baby?"

Simeon Wright, his cousin, heard none of this.

But there is no doubt about what he heard when they left the store, he said in 2005.

Standing on the front porch, Emmett let out a wolf whistle.

Carolyn Donham's whereabouts long have been a mystery, but North Carolina voter rolls list a Carolyn Holloway Donham.

Holloway is her maiden name.

The address is for a green, split-level home in Raleigh at the mouth of a neat cul-de-sac two turns off a busy four-lane thoroughfare.

The well-tended house has burnt-orange shutters and a front-facing brick chimney decorated with a large metal sunburst.

Orange flags emblazed with the word "Google" dot the lawn.

A woman, who appeared to be of late middle age, and a small barking dog appeared at the front door.

When a reporter asked whether this was the Bryant family home, the woman replied, "Yes."

When asked whether Carolyn Donham was at home, the woman replied, "She's not available."

At first, she refused to accept a business card but relented after hearing about the upcoming book.

The Emmett Till Legacy Foundation has shared news reports about the book on Instagram and asked whether Donham would have the "decency and courage" to speak with Till's relatives.