Alan Eugene Miller was scheduled to be executed by lethal injection after a US Supreme Court ruling earlier Thursday vacated a lower court injunction in a long-running dispute over whether Miller would die by that method or nitrogen hypoxia, an untested and unproven method Alabama officials had said they were not ready to use.
"Due to the time constraints resulting in the lateness of the court proceedings, the execution was called off once it was determined the condemned's veins could not be accessed in accordance with our protocol before the expiration of the death warrant," said Alabama Department of Corrections Commissioner John Hamm, according to AL.com.
Miller has been returned to his cell on death row, Hamm said. Gov. Kay Ivey "anticipates that the execution will be reset at the earliest opportunity," her office said in a statement.
Hamm met with the victims' families to notify them of the cancellation before meeting with the press, Ivey said in a statement obtained by CNN.
"Despite the circumstances that led to the cancellation of this execution, nothing will change the fact that a jury heard the evidence of this case and made a decision. It does not change the fact that Mr. Miller never disputed his crimes. And it does not change the fact that three families still grieve," Ivey said.
Untested execution method at issue
The aborted execution attempt followed weeks of legal battles between the state and Miller's attorneys over the method by which he would die -- a fight that ultimately concluded at the Supreme Court.
The inmate had sued the commissioner of the Alabama Department of Corrections, the state attorney general and his warden, alleging corrections officials were moving to execute him by lethal injection after losing paperwork in which he claimed to have chosen to die by nitrogen hypoxia.
The failure to honor his request, Miller's complaint said, violated his constitutional rights.
State officials -- who suggested Miller had made no such choice and that they had no record of his preference -- indicated in court filings they were not ready to use nitrogen hypoxia, which Alabama approved as an alternative execution method in 2018.
The department had "completed many of the preparations necessary for conducting executions by nitrogen hypoxia," but its protocol was "not yet complete," it told CNN last week in a statement. "Once the nitrogen hypoxia protocol is complete, (department) personnel will need sufficient time to be thoroughly trained before an execution can be conducted using this method."
SCOTUS vacates injunction stopping execution
State officials appealed the district court judge's order, asking the US Court of Appeals for the Eleventh Circuit to allow it to move ahead with Miller's execution by lethal injection.
The Eleventh Circuit upheld the lower court's order, writing in a 32-page ruling that the district court had found it was "substantially likely that Mr. Miller submitted a timely election form even though the State says that it does not have any physical record of a form."
But critics and experts reject those arguments, saying there is no proof executions by nitrogen hypoxia would adhere to inmates' constitutional protection against cruel and unusual punishment because it has never been used and could never be ethically tested.
But inmates like Miller are opting for the unproven method due to concerns over the level of pain they might suffer during lethal injection, Robert Dunham, of the Death Penalty Information Center, told CNN: "They are opting for a method that they hope will not be torturous over a method that they are certain will be torturous."
CNN's Ariane de Vogue contributed to this report.