A group of mostly Democratic senators is urging U.S. Attorney General Merrick Garland to release compassionately a Native American activist who is serving a life sentence for his alleged involvement in the 1975 murder of two FBI agents, saying he is suffering from severe health conditions and should be able to live out his remaining days among his own people.

Calls for the release of Leonard Peltier, a citizen of North Dakota's Turtle Mountain Band of Chippewa Indians, have echoed for decades among Native American rights groups. However, pressure on federal officials for clemency for the activist has amped up in the last several years.

Nearly 80 years old, Peltier contracted COVID-19 in 2022 and is suffering from several chronic health conditions, including a potentially fatal abdominal aortic aneurysm, according to Amnesty International.

Calls for Peltier's release have received widespread and growing support from both faith and human rights leaders – including Pope Francis, Saint Mother Teresa, Nelson Mandela, the Dalai Lama and Coretta Scott King, according to the seven lawmakers' letter on Friday to Garland.

In addition, those previously involved in his prosecution, including James H. Reynolds, the U.S. attorney who oversaw the prosecution and appeal of Peltier's case, stated that the "conviction and continued incarceration is a testament to a time and a system of justice that no longer has a place in our society," the lawmakers said.

Peltier was convicted in 1976 for his alleged involvement in the murder of FBI Agents Jack Coler and Ronald Williams on the Pine Ridge Reservation in South Dakota. According to the FBI, Peltier and his supporters claimed that they had traveled to the reservation from Farmington, New Mexico, with a contingent of American Indian Movement members.

The AIM members, according to various Native American activists groups, had gone to the reservation to help quell violence among the political opponents of tribal Chairman Richard Wilson.

Wilson, the groups said, created the Guardians of the Oglala Nation – a private militia that was said to have attacked his political opponents.

Despite evidence of prosecutorial misconduct and due process violations that mounted throughout Peltier's trial, according to the lawmakers' letter, he continues to be detained.

Late U.S. Circuit Court Judge Gerald Heaney, who presided over Peltier's 1986 appeal in the Eighth Circuit, also publicly called for his release – first in 1991 and again in 2000 – detailing the injustice of the trial and proclaiming that "a healing process must begin," according to the lawmakers.

According to Amnesty International, a key witness in the case who is said to have been harassed and threatened for months by the FBI into testifying against Peltier later recanted her testimony. However, she was not allowed to be called as a defense witness at his trial, the nonprofit said.

The Bureau of Prisons allows its director to grant a reduction in sentence, or compassionate release, to prisoners that meet certain criteria, including advanced age and deteriorating health, according to the lawmakers' letter.

"If the director of the BOP approves a compassionate release, and the Parole Commission agrees, Mr. Peltier could be released immediately," they said.

The recent call for Peltier's release isn't the first time federal lawmakers have urged clemency for the Native American activist.

Thirty-three members of Congress in October 2023 called upon the Biden administration to grant Peltier's clemency, saying key figures involved in his prosecution have stepped forward during the course of his incarceration that underscored the constitutional violations and prosecutorial misconduct that took place during the investigation and trial that led to his conviction.

"Now, more than ever, bedrock principles of justice warrant your consideration of a grant of executive clemency or support of compassionate release at the Federal Bureau of Prisons," the members told the administration.

U.S. Sens. Brian Schatz and Mazie K. Hirono of Hawaii, Elizabeth Warren and Edward J. Markey of Massachusetts, Tina Smith of Minnesota and Peter Welch of Vermont, all Democrats, penned the letter, in addition to Bernie Sanders, an Independent of Vermont.