James Harvey Callahan, set to die early Thursday evening, was granted a stay, Holman prison warden Grantt Culliver told officers on death row. The Supreme Court's brief order did not detail why it granted the stay.
It would have been the first U.S. execution since September, when the high court agreed to consider whether lethal injection is cruel and unusual punishment. The inmate's attorney had asked the high court to halt the execution after a federal appeals court lifted a stay granted by a Montgomery judge.
Callahan was sentenced to death for the 1982 murder of Jacksonville State University student Rebecca Suzanne Howell, who was abducted from a coin laundry and raped before being strangled and dumped in a creek.
Her mother, Verna Coheley, and sister, Karen Greer, had arrived to witness the execution. A corrections officer quoted them as saying it was "cruel and unusual" for them to get there only to learn of the stay, said prison system spokesman Brian Corbett.
The Supreme Court on Sept. 25 agreed to hear a challenge filed by two Kentucky death row inmates over that state's lethal injection method. No U.S. executions have taken place since then, except for one that occurred in Texas just hours after the decision was made.
Courts have put off several executions pending the Kentucky case, including that of Alabama death row inmate Tommy Arthur. He was to have been put to death at Holman prison near Atmore on Dec. 6, but the Supreme Court stopped the execution a day earlier.
Callahan challenged Alabama's method of lethal injection, which like most capital-punishment states is similar to Kentucky's. The Atlanta-based 11th U.S. Circuit Court of Appeals ruled Tuesday, however, that he waited too long to do so.
In its 2-1 ruling lifting a lower-court judge's Dec. 14 stay, the appeals court said it did not make any finding on "the relative merits of Callahan's constitutional claim because we conclude the claim is barred by the statute of limitations."
The Supreme Court heard oral arguments in the Kentucky case Jan. 7; a ruling is unlikely before spring.
Kentucky death row inmates Ralph Baze and Thomas Clyde Bowling Jr. claim that lethal injection as practiced by the state amounts to cruel and unusual punishment, in violation of the Eighth Amendment.
Lethal injections, devised as a humane alternative to electrocution and the gas chamber, have come under attack in recent years amid reports that the three-drug cocktail doesn't always work as quickly as intended and that inmates are subjected to excruciating pain before they die.
Callahan, who has been on death row for more than a quarter-century, met with a half-dozen relatives, including two sisters and his son, as the hour of the execution approached. He had only a cheeseburger and a Coke for what could have been his last meal.
Corbett, the Department of Corrections spokesman, said Callahan appeared confident he would get a stay but was "anxious" at times.
The warden said family members were "overjoyed and applauded when told of the stay."
Separately Thursday, a young man who says he fatally shot a retired police officer in 2003 because he thought the "A" on the victim's cap meant he was the Antichrist had his death sentence reduced by the Florida Supreme Court.
The justices unanimously ordered that Ryan Green, 24, be sentenced to life in prison without parole based on evidence of schizophrenia. A Pensacola jury had rejected his insanity plea in convicting Green of first-degree murder, but he appealed only his sentence.