An NPR investigation has uncovered new evidence in a prominent unsolved murder case from the civil rights era, including the identity of an attacker who admitted his involvement but was never charged.

The murder of Boston minister James Reeb in 1965 drew national attention at the time and spurred passage of the Voting Rights Act, which outlawed the Jim Crow voting practices that had disenfranchised millions of black Americans.

The case remains officially unsolved. Three men charged in 1965 with attacking Reeb and two other ministers on a street corner in Selma, Ala., were acquitted by an all-white jury.

But a four-year NPR investigation, led by Alabama-based reporters Chip Brantley and Andrew Beck Grace, found an eyewitness to the attack who has never spoken publicly about what she saw. She said the three men acquitted in the case — Elmer Cook, William Stanley Hoggle and Namon O'Neal "Duck" Hoggle — were, in fact, the men who attacked Reeb.

That witness, Frances Bowden, also described the participation of another man, William Portwood. In an exclusive interview with NPR, Portwood confirmed his participation in the 1965 assault.