ANGOLA, La. (CNN) — Albert Woodfox, who’s spent more than four decades in solitary confinement for a crime he’s long argued he didn’t commit, might soon set foot outside prison.

U.S. District Judge James J. Brady ruled Monday that Woodfox, 68, should be released from prison and should not face a third trial due to “exceptional circumstances,” including his age and poor health and the court’s “lack of confidence in the state to provide a fair third trial.”

Woodfox, 68, is the last imprisoned member of the so-called Angola 3, prisoners who were accused in the 1972 killing of guard Brent Miller at the Louisiana State Penitentiary at Angola.

Woodfox — who was originally imprisoned on an armed robbery conviction — has said he had tried to point out injustices at the prison and was targeted and wrongfully accused because of his activism as a Black Panther.

Robert King, another one of the “Angola 3,” was freed after his conviction in the killing of a fellow inmate was overturned in 2001.

The same went for Herman Wallace, who was released in 2013 after a judge vacated his murder conviction and sentence. He only experienced a few days of freedom; he was suffering from terminal liver cancer and died just days later.

A federal appeals court overturned Woodfox’s conviction last year. But he’s remained behind bars and is awaiting a third trial.

That’s where he should stay, a spokesman for the Louisiana Department of Justice told The Times-Picayune Monday.

“With today’s order, the Court would see fit to set free a twice-convicted murderer who is awaiting trial again for the brutal slaying of Corrections Officer Brent Miller,” spokesman Aaron Sadler said, according to the New Orleans newspaper.

The Louisiana attorney general’s office is seeking an emergency stay to block the judge’s decision, he said, and “make sure this murderer stays in prison and remains fully accountable for his actions.”

Woodfox’s attorneys, George Kendall and Carine Williams, are demanding that their client be released immediately, especially now that prosecutors have failed in two attempts to secure a valid conviction.

“Now, because the State’s key witnesses are deceased, and Mr. Woodfox’s alibi witnesses are also deceased, there is no practical way for there to be a third trial which comports with the standards of a fair, American trial,” the attorneys’ statement said.

Amnesty International praised the judge’s decision as a “momentous step toward justice.”

“Woodfox has spent 43 years trapped in a legal process riddled with flaws,” said Jasmine Heiss, a senior campaigner for the human rights group. “The only humane action that the Louisiana authorities can take now is to ensure his immediate release.”

Louisiana Attorney General James Caldwell has repeatedly stood by Woodfox’s conviction, and in 2013 he released a statement in response to a petition, letters and emails submitted on Woodfox’s behalf. In it, he rejected claims of Woodfox’s innocence, as well as assertions that he was held in solitary confinement.

Rather, Caldwell said, Woodfox was being held in a lockdown known as “closed cell restricted,” which he said was designed to protect prisoners and guards. Watchdog groups say CCR still constitutes solitary.

“Contrary to popular lore, Woodfox and Wallace have never been held in solitary confinement while in the Louisiana penal system,” Caldwell wrote in 2013. “They have always been able to communicate freely with other inmates and prison staff as frequently as they want. They have televisions on the tiers which they watch through their cell doors.”

They also have radios, headsets, stamps and reading and writing material, he said, and their privileges include shopping at the prison canteen for grocery and personal hygiene items, thrice-weekly trips outside for sun and exercise, regular visitations, and an hour outside their cells each day to shower, chat on the phone or talk to other inmates.

King, however, feels he spent 29 years in solitary before his 2001 release. He now serves as an adviser for Solitary Watch, a project devoted to research and reporting on solitary confinement. He told CNN last year he still has issues with orientation after more than a generation in a 6-by-9-by-12-foot cell.

“I get confused as to where I am, where I should be,” he said. “The brain somehow won’t register things, and it won’t register exactly where I am.”

Law enforcement experts say solitary confinement is an effective tool for keeping prisoners and guards safe — and for avoiding lawsuits, when you consider that prison officials could be deemed liable if they’re found to have ignored the risks of placing a gang member, predator or other violent inmate into the general population with other prisoners.

The National Alliance on Mental Illness says solitary was deemed controversial as early as the 1890s, but the practice expanded in the 1970s, along with the U.S. prison population and the “proportion of prisoners suffering from serious mental illnesses.” The spike in the construction of “supermax” penitentiaries, where it’s more common to house prisoners in isolation, also bolstered the numbers, as corrections officers increasingly responded to “violence and ‘acting out’ — behavior they do not understand — by isolating prisoners in lockdown,” NAMI says.

Several watchdog groups, including Amnesty International, estimate that as many 80,000 American prisoners are in solitary confinement, and 25,000 are held in long-term isolation. That means they spend at least 22 hours daily in their windowless cells, typically no larger than 8 by 10 feet, and experience only minimal human contact.

More than a quarter of the prison population suffers from mental illness, NAMI reports, well above the norm for average Americans. And while extreme isolation has been linked to anxiety and depression, Peter Scharff Smith of the Danish Institute for Human Rights wrote in an essay that prisoners also complain of “anger, hatred, bitterness, boredom, stress, loss of the sense of reality, suicidal thoughts, trouble sleeping, impaired concentration, confusion, depression, and hallucinations,” along with headaches, heart palpitations, increased pulse, oversensitivity to stimuli, dizziness, loss of appetite and weight loss.

“The widespread consensus among mental health professionals is that solitary confinement, for the overall majority of mentally ill prisoners, places them at severe risk of additional harm,” said Craig Haney, director of the program in legal studies at the University of California, Santa Cruz, and an expert on solitary confinement.

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