A grand jury in Mississippi declined to indict a white woman whose accusation that black teenager Emmett Till propositioned her in 1955 led to his abduction and murder.
The horrific murder of the 14-year-old helped to spark the civil rights movement in the US.
The grand jury decided after seven hours of deliberation that there was insufficient evidence to indict Carolyn Bryant Donham of complicity in his kidnap and murder, said Dewayne Richardson, the prosecutor for Leflore County.
The 87-year-old was 21 at the time of Till's killing.
The decision came a month after an unserved arrest warrant from the time of the crime was found in the basement of the Leflore County courthouse for Ms Donham, her husband Roy Bryant and his half-brother JW Milam.
The two men, both now deceased, were arrested and acquitted on murder charges by an all-white jury, but Ms Donham was never taken into custody.
The pair later admitted in a magazine interview that they had killed the boy.
Last month, US media reported that an unpublished memoir written by Ms Donham claimed she was unaware that Till would be tortured and murdered.
In her account, she said the men brought the boy to her in the middle of the night and she denied it was him, but that he himself admitted it.
In 2004, the US Justice Department had reopened the investigation, but was unable to press any charges due to the statute of limitations.
In 2017, the author of a book on the case said Ms Donham had confessed that Till had never made any advances.
The Justice Department reopened the file again, but investigators failed to determine whether she had invented the incident or not, and the investigation was closed again in December 2021.
Till, who lived in Chicago, was visiting relatives in Mississippi when he and some other local children visited the shop owned by the Bryants, where Ms Donham was working alone.
She said at the time he had propositioned her and touched her on the arm, hand and waist.
His disfigured body was found a few days later in a river.
The decision by his mother to have the body displayed in an open casket at the funeral brought home the horrors of lynchings and discrimination in the American south, and helped trigger the civil rights movement of the 1950s and 1960s.
Till's cousin, Reverend Wheeler Parker Jr, told CBS News that the decision was "unfortunate but predictable" after "hundreds of years of anti-black systems that guaranteed those who killed Emmett Till would go unpunished, to this day".
In March, a new law named after Till came into effect making racist lynchings a federal crime with a punishment of up to 30 years in prison.
