*This story has been updated with the Supreme Court justice's action.
BONNE TERRE — U.S. Supreme Court Justice Samuel Alito has issued an order halting the planned execution of a Missouri inmate.
Alito's order issued late Tuesday does not explain why he suspended the scheduled execution of Russell Bucklew, but it indicates that he or the high court will have more to say about the matter.
The order was issued shortly after the full 8th U.S. Circuit Court of Appeals lifted a stay of execution granted hours earlier by a three-judge panel of that court, which cited concerns about the inmate's rare medical condition that could cause pain and suffering during lethal injection.
Russell Bucklew was scheduled to die at 12:01 a.m. Wednesday for killing a southeast Missouri man in 1996.
"Bucklew's unrebutted medical evidence demonstrates the requisite sufficient likelihood of unnecessary pain and suffering beyond the constitutionally permissible amount inherent in all executions," the ruling from the 8th U.S. Circuit Court of Appeals read.
Bucklew, 46, suffers from a rare condition that causes weakened and malformed veins.
Cheryl Pilate, an attorney for Bucklew, said she was "relieved" by the ruling, though it doesn't necessarily mean the execution is off. The panel's ruling could be overturned by the full appeals court, or by the U.S. Supreme Court.
In a dissenting opinion, appeals court Judge James Loken said Bucklew's medical evidence "simply does not satisfy the Supreme Court's rigorous standards" for a stay of execution.
Wednesday's execution would be the first in the nation following a botched lethal injection last month in Oklahoma.
Bucklew was scheduled to receive a lethal injection at 12:01 a.m. Wednesday for killing a southeast Missouri man during a violent crime spree in 1996.
Gov. Jay Nixon, a Democrat and proponent of the death penalty, told The Associated Press on Monday that while he was still considering Bucklew's clemency request, he hadn't seen a reason to intervene.
"This guy committed very, very heinous crimes and while it's a difficult and challenging part of this job, we'll continue to move forward unless a court says otherwise," Nixon said.
Bucklew has a congenital condition known as cavernous hemangioma that causes weakened and malformed blood vessels, as well as tumors in his nose and throat. His attorneys say he could experience great suffering during the execution process, and Bucklew told the AP by phone last week that he is scared of what might happen.
None of the six inmates executed since Missouri switched to pentobarbital last year have shown outward signs of pain or suffering. But when Oklahoma inmate Clayton Lockett's execution went awry on April 29, it prompted renewed concern over lethal injection.
Lockett's vein collapsed and he died of an apparent heart attack 43 minutes after the start of the punishment. Oklahoma put on hold a second execution scheduled for the same night as Lockett's death, while the state investigates what happened.
European companies have cut off supplies of certain execution drugs because of opposition to capital punishment, causing states, including Missouri, to turn to U.S. sources, including compounding pharmacies. The states refuse to identify the sources of their execution drugs, saying the secrecy is necessary to protect the sources from possible retaliation by death penalty opponents.
Death penalty opponents say the secrecy makes it impossible to ensure that the drugs couldn't cause an inmate to endure an agonizing death that rises to the level of unconstitutionally cruel and unusual punishment.
In addition to the stay request, a federal court is considering a request to allow Bucklew's lawyers to record the execution on video.
Nixon said the Missouri Department of Corrections works "very hard to make sure this challenging responsibility is handled as humanely as possible."
The AP and four other news organizations filed a lawsuit last week against the Missouri Department of Corrections, claiming the state's refusal to provide information on the execution drug violates the public's constitutional right to have access to information about the punishment.
According to prosecutors, Bucklew was angry at his girlfriend, Stephanie Pruitt, for leaving him, and his threats led her to move with her two daughters into the Cape Girardeau home of another man, Michael Sanders, who had two sons. Bucklew tracked Pruitt down at Sanders' home on March 21, 1996, and killed Sanders in front of her and the four children. He handcuffed and beat Pruitt, drove her to a secluded area and raped her.
Later, after a state trooper spotted the car, Bucklew shot at the trooper but missed, authorities say. Bucklew was grazed in the head and hospitalized. He later escaped from jail, hid in the home of Pruitt's mother and beat her with a hammer. She escaped and Bucklew was arrested a short time later.
Pruitt later married and was killed by her husband in a murder-suicide in 2009.