Leonard Peltier was denied parole on Tuesday, meaning theres likely only one other way the ailing, 79-year-old Native American rights activist will ever be released after serving nearly 50 years in prison: If President Joe Biden intervenes and commutes his sentence.

Peltier has been in prison since 1977 when the U.S. government convicted him for killing two FBI agents in a 1975 shoot-out on Pine Ridge Reservation in South Dakota.

But his trial was full of misconduct, including federal prosecutors hiding evidence that exonerated Peltier and the FBI threatening and coercing witnesses into lying. The governments case fell apart after these revelations, so it abruptly revised its charges against Peltier to aiding and abetting whoever did kill those agents on the grounds that he was one of dozens of people present when the shoot-out occurred.

There was never evidence that Peltier committed a crime. The FBI and U.S. attorneys office never did figure out who killed those agents.

Peltier is widely considered Americas longest-serving political prisoner .

Todays announcement continues the injustice of this long ordeal for Leonard Peltier, said Kevin Sharp, Peltiers attorney. This decision is a missed opportunity for the United States to finally recognize the misconduct of the FBI and send a message to Indian Country regarding the impacts of the federal governments actions and policies of the 1970s.

Sharp, who is also a former federal judge appointed during Barack Obama s presidency, said he will immediately appeal to the Parole Commissions appeals board and in federal court.

I have not lost hope that Leonard Peltier will one day be free, said Sharp.

The FBI continues to oppose Peltiers release and is the main reason, if not the only reason, that hes still in prison. But its stated reasons for opposing Peltiers release are full of holes, outdated and remarkably easy to disprove .

The FBI also has not publicly addressed the key context of that 1975 shoot-out: That the FBI itself was intentionally fueling tensions on that reservation as part of a covert campaign to suppress the activities of the American Indian Movement, or AIM, a grassroots movement for Indigenous rights. Peltier was an active AIM member and an FBI target.

Today is a sad day for Indigenous Peoples and justice everywhere, Nick Tilsen, president and CEO of NDN Collective, an Indigenous-led advocacy group, said in a statemet.

They denied parole to a survivor of genocidal Indian boarding schools and as he struggles to survive his unjust incarceration, they insist on holding him for a crime for which they have no physical evidence against him, said Tilsen. Clearly, the Parole Commission which is supposed to be an independent body was influenced by the FBI.

Peltier has maintained his innocence the entire time hes been in prison. It has almost certainly contributed to him being denied parole.

Prior to Tuesday, the last time Peltier was denied parole was in 2009. He is unlikely to live long enough to try for parole again, given the yearslong process involved, his advanced age and his poor health. Peltier has diabetes and an aortic aneurysm.