Seventy-one-year-old Louisiana prisoner Herman Wallace, who spent 41 years in solitary confinement and is now dying of cancer, was released from prison on Tuesday night.

US District Chief Judge Brian Jackson denied a state motion seeking to stop him overturning Mr Wallace's 1974 murder conviction in the death of prison guard Brent Miller.

Mr Wallace and two other inmates convicted of the slaying came to be known as the "Angola Three."

Mr Wallace was serving a 50-year armed robbery sentence when the guard was stabbed in 1972.

Amnesty International USA delivered a petition to Louisiana Governor Bobby Jindal, containing 65,000 signatures calling the men's solitary confinement inhuman and degrading.

"Tragically, this step toward justice has come as Herman has only days or hours left to live," said Amnesty executive director Steven Hawkins.

"No ruling can erase the cruel, inhuman and degrading prison conditions he endured for more than 41 years."

Mr Wallace's lawyers said the decision gave "some measure of justice after a lifetime of injustice."

"It is Mr Wallace's hope that this will help ensure that others including his lifelong friend and fellow Angola Three member Albert Woodfox do not continue to suffer such cruel and unusual confinement," they added.

Mr Woodfox and Mr Wallace always denied involvement in the killing, claiming they were targeted for helping establish the Black Panthers at the prison in 1971 and setting up demonstrations for better conditions.