Relatives of black teenager Emmett Till, brutally lynched in 1955, have joined with supporters asking authorities to reverse their decision to close an investigation of the crime.

Instead they want a white woman at the centre of the case to be prosecuted.

Authorities have known for decades that Carolyn Bryant Donham, now in her 80s and living in North Carolina, played a key role in Till’s slaying, and they need to act immediately to bring her to justice before time runs out, said Deborah Watts, a cousin of Till.

“Time is not on our side,” Watts, who heads the Emmett Till Legacy Foundation, said during a news conference.

Relatives presented Mississippi authorities with a petition signed by about 250,000 people seeking a renewed probe of the killing, which came to demonstrate the depth of racial hatred in the South to the world. Other petition drives continue.

Michelle Williams, chief of staff for Mississippi Attorney General Lynn Fitch, cast doubt on the possibility of a renewed investigation. In a statement, she said the Justice Department had worked with a local district attorney’s office in a re-examination that ended in December.

“This is a tragic and horrible crime, but the FBI, which has far greater resources than our office, has investigated this matter twice and determined that there is nothing more to prosecute,” Williams said.

The Justice Department announced in December it was ending its renewed investigation into the killing of Till, a 14-year-old from Chicago who was abducted, tortured and killed after witnesses said he whistled at Donham, then known as Carolyn Bryant, at a family store where she worked in rural Money, Mississippi.

Federal officials reopened the investigation after a 2017 book quoted Donham as saying she lied when she claimed Till accosted her.

Relatives have publicly denied that Donham recanted her allegations, and Donham told the FBI she had never changed her story, the Justice Department said.

The Justice Department also said historian Timothy B. Tyson, author of The Blood of Emmett Till, was unable to produce recordings or transcripts to substantiate his account of Donham allegedly admitting to lying about her encounter with the teen.

Donham’s then-husband, Roy Bryant, and his half-brother J.W. Milam, were tried on murder charges about a month after Till was killed, but an all-white Mississippi jury acquitted them. Months later, they confessed in a paid interview with Look magazine.

The Justice Department found Bryant and Milam were not the only people involved, however, and estimates on the number of people who might have played a role in Till’s killing range from from a half-dozen to more than 14.

On Monday, Congress gave final approval to legislation that for the first time would make lynching a federal hate crime, sending the bill to President Joe Biden.

Years in the making, the Emmett Till Anti-Lynching Act is among some 200 bills that have been introduced over the past century that have tried to ban lynching in the US.

– AAP