(CNN) Could Albert Woodfox, who's spent more than four decades in solitary confinement for a crime he's long argued he didn't commit, set foot outside prison this week?

The decision about whether the last imprisoned member of the so-called Angola 3 goes free is in the hands of a federal appeals court.

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."

But Louisiana's attorney general appealed the ruling, insisting that Woodfox is guilty of killing a Louisiana prison guard and should remain in prison.

The 5th Circuit Court of Appeals hasn't decided the case yet. But it has set a new deadline: Woodfox's release, judges ruled Tuesday, will be temporarily blocked at least until 1 p.m. Friday.

Woodfox and Herman Wallace were accused in the 1972 killing of guard Brent Miller at the Louisiana State Penitentiary at Angola. A third inmate, Robert King, was linked to Miller's death but never charged.

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The group became known as the "Angola 3," and the case has been a cause celebre for years, with activists arguing there is no evidence tying the three men to the crime and decrying the decades they each spent in solitary confinement.

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

King was freed after his conviction in the killing of a fellow inmate was overturned in 2001.

Herman Wallace was released from prison after a judge vacated his murder conviction and sentence. He died days later.

AG balks

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

Woodfox's attorneys, George Kendall and Carine Williams, are demanding 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."

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.

'I get confused'

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.