Alabama executes Alan Eugene Miller with nitrogen gas for 1999 killings

Alabama carried out the second-ever nitrogen gas execution in the United States on Thursday.

Alan Eugene Miller, 59, was sentenced to death for the 1999 murders of his then-coworkers Lee Holdbrooks and Christoper Scott Yancy, and his former supervisor Terry Lee Jarvis.

Miller was executed after 6 p.m. CT at the William C. Holman Correctional Facility, a state prison in Atmore, Alabama. His time of death, according to Gov. Kay Ivey's office, was 6:38 p.m.

"Justice has been served," Alabama Attorney General Steve Marshall said in a statement. "After two decades, Alan Miller was finally put to death for a depraved murder spree that cruelly took the lives of three innocent men.

"I ask the people of Alabama to join me in praying for the families and friends of the victims, that they might now find peace and closure," Marshall's statement concluded.

Miller was initially sentenced to be executed in September 2022 via lethal injection, but it was called off after officials had trouble inserting an intravenous line to administer the fatal drugs and were concerned they would not be able to do so before the death warrant expired.

Prior to the botched execution, the state had considered carrying out the death sentence via nitrogen hypoxia, according to the Death Penalty Information Center, a nonprofit that provides data and analysis on capital punishment.

In November 2022, Alabama officials agreed not to execute Miller by lethal injection again but said if they made a second effort, the state would use nitrogen hypoxia as the method, the DPIC said.

In May 2024, the Alabama State Supreme Court agreed to let the Department of Corrections carry out Miller's death sentence by nitrogen hypoxia.

It comes after Alabama became the first state to execute a prisoner, Kenneth Eugene Smith, by nitrogen gas in January of this year.

Nitrogen hypoxia is the term for a means of death caused by breathing in enough nitrogen gas to deprive the body of oxygen -- in this case, intended to be used as a method of execution.

The protocol in Alabama calls for an inmate to be strapped to a gurney and fitted with a mask and a breathing tube. The mask is meant to administer 100% pure nitrogen, depriving the person of oxygen until they die.

About 78% of the air that humans breathe is made up of nitrogen gas, which may lead people to believe that nitrogen is not harmful, according to the U.S. Chemical Safety Board.

However, when an environment contains too much nitrogen and the concentration of oxygen becomes too low, the body's organs, which need oxygen to function, begin shutting down and a person dies.

State officials have argued death by nitrogen gas is a humane, painless form of execution and that the person would lose consciousness within seconds of inhaling the nitrogen and die within minutes.

However, Smith's execution took 22 minutes from the time the curtains of the viewing room opened and closed, according to the Associated Press, during which Smith reportedly shook and writhed on the gurney, pulling against the restraints "for at least two minutes" before he began breathing heavily and ultimately passed away.

Three states -- Alabama, Mississippi and Oklahoma -- have approved nitrogen gas as a form of execution and Ohio lawmakers introduced a bill earlier this year to allow execution by nitrogen gas.

However, medical and legal experts have told ABC News that nitrogen gas as a method for execution is untested and there's no evidence the method is any more humane or painless than lethal injection.

Dr. Joel Zivot, an associate professor in the department of anesthesiology at Emory University School of Medicine, said he reviewed Smith's autopsy which showed blueness of the skin, pulmonary congestion and edema, which he says indicated that he died from being asphyxiated "slowly and painfully."

"If that's what Alabama thinks is a job well done, well then there seems to be a wide disagreement on what a job well-done means," he told ABC News. "So, if this is again, what they intend, then they intend to kill him cruelly, and they will intend to kill Alan Miller in the same cruel way."

Zivot has previously reported analyzing autopsies after lethal injection cases and reports finding that many show signs of pulmonary edema. In 2020, NPR said it expanded this work by analyzing over 200 autopsies after lethal injection and reported that signs of pulmonary edema were mentioned in 84% of the cases it reviewed.

Attorney General Steve Marshall described Smith's execution as "textbook" but Zivot said it's hard to describe nitrogen hypoxia as "textbook" and that it's a "proven method" when it's never been a tested method.

"I recognize that [people were] murdered and that what is at stake here is a very, very serious problem," he said. "We're not saying that Kenneth Smith or Alan Miller have become saint-like men as they have been incarcerated. It doesn't matter whether they're good or bad at this point with respect to how their punishment should be delivered. That doesn't give us license to torture them."