U.S.'s Alabama completes first execution using nitrogen gas asphyxiation

The southern U.S. state of Alabama on Thursday night completed the country's first execution using nitrogen gas asphyxiation, according to a news release from Alabama Governor Kay Ivey.

Inmate Kenneth Smith, a 58-year-old convicted of a 1988 murder and sentenced to death, died at 8:25 p.m. local time (0225 GMT Friday) at an Alabama prison after breathing pure nitrogen gas through a face mask to cause oxygen deprivation, authorities said.

Smith appeared to remain conscious for several minutes after the nitrogen was activated, according to five journalists who were allowed to watch the execution through glass as media witnesses. Although the mask was also secured to the gurney, he then began shaking his head and writhing for about two minutes, and then could be seen breathing deeply for several minutes before his breathing slowed and became imperceptible, the witnesses said.

"It appeared that Smith was holding his breath as long as he could," Alabama Corrections Commissioner John Hamm told a press conference. "He struggled against the restraints a little bit but it's an involuntary movement and some agonal breathing. So that was all expected."

Earlier on Thursday, the U.S. Supreme Court denied a last-minute appeal by Smith's lawyers to halt the execution, who argued such a method would violate constitutional protections against cruelty.

Three liberal Justices, Elena Kagan, Ketanji Brown Jackson and Sonia Sotomayor, issued a written dissent saying they would have paused the execution. The majority justices did not issue any statements.

Smith also brought separate claims before a federal court of appeals trying to put the execution on hold, which were declined in a 2-1 decision issued later on Wednesday.

It was the first nitrogen hypoxia execution nationwide. Alabama botched its previous attempt to execute him by lethal injection in November 2022.

Human rights groups, United Nations torture experts and lawyers for Smith had sought to prevent it, saying the method was risky, experimental and could lead to an agonizing death or non-fatal injury.

"If Alabama proceeds with its planned execution attempt, it will be only the second time in U.S. history that a state follows through with a second execution attempt after a previous, failed attempt," Smith's lawyers wrote in court filings.

Smith's lawyers argued that if the mask were a poor fit, it could allow oxygen in and prolong Smith's suffering, or if he becomes nauseous, he could be "left to choke on his own vomit," according to U.S. media.

The untested method of capital punishment is controversial. Supporters said the method would be humane, but critics called it cruel and experimental.

Oklahoma and Mississippi are the only other states to approve nitrogen for executions

(With input from agencies)