UNITED STATES indigenous activist Leonard Peltier, who was convicted of the 1975 killings of two FBI agents in South Dakota, was set to appear at a parole hearing today at a federal prison in Florida.

At 79, his health is failing, and if this parole request is denied, it might be a decade or more before it is considered again, said his attorney Kevin Sharp, a former federal judge. 

Mr Sharp and other supporters have long argued that Mr Peltier was wrongly convicted and say now that this effort may be his last chance at freedom.

“This whole entire hearing is a battle for his life,” said Nick Tilsen, president and CEO of the NDN Collective, an indigenous-led advocacy group. “It’s time for him to come home.”

The fight for Peltier’s freedom, which is embroiled in the indigenous rights movements, remains so robust nearly half a century later that “Free Peltier” T-shirts and caps are still sold online.

But the FBI and its current and former agents dispute the claims of innocence. 

Mike Clarke, president of the Society of Former Special Agents of the FBI, has written a letter arguing that Mr Peltier should remain incarcerated, referring to him as a “cold-blooded murderer.”

Mr Peltier, a member of the Turtle Mountain Chippewa tribe, was active in the American Indian Movement (AIM), which began in the 1960s as a local organisation in Minneapolis that grappled with issues of police brutality and discrimination against Native Americans. 

On June 26, 1975 FBI agents came to the Pine Ridge reservation to serve arrest warrants amid ongoing battles over Native treaty rights and self-determination.

FBI agents Jack Coler and Ronald Williams were shot in the head at point-blank range. Also killed in the shoot out was AIM member Joseph Stuntz. 

Mr Peltier was convicted and sentenced in 1977 to life in prison, despite defence claims that evidence against him had been falsified.