Updated

If the state of Missouri intends to execute a man who raped his ex-girlfriend after killing her new beau in front of four children, it may have to find a method that doesn’t cause Russell Bucklew “unnecessary pain.”

U.S. Supreme Court Associate Justice Samuel Alito, who handles emergency appeals from Missouri, suspended Bucklew’s execution Tuesday night an hour before the convicted killer was to die by lethal injection. Alito’s ruling came after the federal 8th Circuit Court of Appeals found that a rare medical condition suffered by Bucklew means that he will likely experience "unnecessary pain and suffering beyond the constitutionally permissible amount inherent in all executions."

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Bucklew was scheduled to be executed at 12:01 a.m. Wednesday. After Alito’s eleventh-hour ruling, which did not endorse the lower court’s holding, Missouri Attorney General Chris Koster issued a statement saying his office understands the full U.S. Supreme Court would consider Bucklew's requests on Wednesday.

Under Missouri law, the state has 24 hours to carry out a death warrant, meaning it could still execute Bucklew any time on Wednesday if the high court rejects his appeals. If the execution happens Wednesday, it would be the first in the nation since a botched lethal injection in Oklahoma last month that left a man convicted of shooting and burying a woman alive writhing on a gurney before he died of a heart attack more than 40 minutes after the procedure began.

Bucklew, 46, 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 Associated Press by phone last week that he is scared of what might happen.

"The state does not have the right to inflict extreme, torturous pain during an execution," attorney Cheryl Pilate said. "We still hope that Mr. Bucklew's grave medical condition and compromised airway will persuade the governor or a court to step back from this extremely risky execution."

Bucklew's hopes rest with the courts, as Missouri Gov. Jay Nixon, a Democrat and a proponent of the death penalty, rejected Bucklew's clemency request late Tuesday.

"The jury in this case properly found that these heinous crimes warranted the death penalty, and my denial of clemency upholds the jury's decision," he said.

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.

According to prosecutors, Bucklew was angry at his girlfriend, Stephanie Pruitt, for leaving him. Pruitt moved with her two daughters into the Cape Girardeau home of Michael Sanders, who had two sons. Bucklew tracked Pruitt down at Sanders' home March 21, 1996, and killed Sanders in front of Pruitt 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.

The Associated Press contributed to this report