Geneva, Switzerland - Calls for the release of imprisoned Indigenous freedom fighter Leonard Peltier resounded at the 139th session of the United Nations Human Rights Committee.

Expanding Indigenous rights and ending extreme sentencing practices were central themes at this year's review of the United States by the UN Human Rights Committee, with the case of Leonard Peltier, the country's longest-held political prisoner, featuring prominently in the proceedings.

A member of the Turtle Mountain Band of Chippewa, Peltier was taken into US custody after he was convicted of killing two FBI agents in a shootout on the Pine Ridge Indian Reservation in South Dakota in June 1975. He was sentenced to two terms of life imprisonment and is currently incarcerated in a maximum-security facility in Coleman, Florida.

There is no evidence to justify locking Peltier up for nearly five decades and repeatedly denying him parole, his supporters say. Records suggest the FBI coerced witnesses and excluded and falsified evidence in the 1977 murder trial. Even the top prosecutor in the case, former US Attorney James Reynolds, has called for the American Indian Movement icon's release.

Dr. Changrok Soh of South Korea, vice chair of the Human Rights Committee, agreed with Indigenous representatives in Geneva that Peltier's long imprisonment raises grave concerns. On Tuesday, he asked the US delegation to clarify: "Civil society shadow reports have noted that 'death by incarceration' continues to disproportionately impact Black and Indigenous Peoples in the US. Can the state party describe what it is doing regarding life sentences for political prisoners, in particular, the case of Indigenous political prisoner Leonard Peltier, who is now – at 79 years old – the longest serving US political prisoner and has served 48 years in prison?"

A representative of the Department of Justice on Wednesday said the US government cannot answer the question, as there is a pending clemency petition for Peltier.

President Joe Biden has the authority to grant clemency to Peltier without congressional approval, but he has so far not chosen to take that step.

Fed up with the US government's failure to adequately address their concerns, civil society NGOs and human rights advocates in Geneva sent a letter to the Department of Justice on Wednesday calling for action to right the grave wrongs committed against Peltier and others held under unjust prison sentences.

The letter – signed by Water Protector Legal Collective, the Center for Constitutional Rights, the Abolitionist Law Center, and more – urges the federal government to commit to "ending life sentences that amount to death by incarceration disproportionately for Black, Brown and Indigenous communities."

Advocates also demanded the Biden administration grant clemency to Peltier and invite the UN Special Rapporteur for Indigenous Peoples to visit the US to study his case and the status of Indigenous communities around the country.

"Leonard’s continued incarceration is an open wound for Indigenous Peoples and a visible blemish on the United States' human rights record," the signatories wrote.