He was the last survivor of three Klansmen who were convicted, years later, in the killing four black girls in 1963, a case that was a turning point in the civil rights struggle.

After Mr. Blanton’s conviction in 2001, Bill Baxley, who had prosecuted Mr. Chambliss as Alabama’s attorney general in 1977, wrote an angry opinion article in The New York Times asserting that the F.B.I. had not been forthcoming in the Chambliss case and had not revealed the existence of the tapes.

“For more than two decades, Mr. Blanton and Mr. Cherry evaded indictment and prosecution because the F.B.I. held back these recordings,” Mr. Baxley wrote. “This was evidence we desperately needed in 1977 — evidence whose existence F.B.I. officials had denied. Had it been provided in 1977, we could have convicted all three of these Klansmen.”

nytimes.com