Convicted murderer Kenneth Smith, who survived an earlier execution attempt by lethal injection, was killed on Thursday night.
Kenneth Smith, a convicted murderer, has become the first person to be executed by asphyxiation with nitrogen gas in the United States.
Officials said 58-year-old Smith was pronounced dead at 8:25pm on Thursday (02:25 GMT on Friday) at Holman Correctional Facility in Alabama after breathing pure nitrogen gas through a face mask to cause oxygen deprivation.
His death marks the first time that a new execution method has been used in the United States since lethal injection, now the most commonly used method, was introduced in 1982.
Alabama has called its new protocol “the most painless and humane method of execution known to man”.
The last US execution using gas was in 1999 when a convicted murderer was put to death using hydrogen cyanide gas.
Alabama is one of three US states that have approved the use of nitrogen hypoxia as a method of execution, along with Oklahoma and Mississippi.
United Nations human rights experts and lawyers for Smith, who survived Alabama’s previous attempt to execute him by lethal injection, had sought to prevent it, saying the method was risky and could lead to a torturous death or nonfatal injury.
Smith’s execution took about 22 minutes, and he appeared to shake and writhe on the gurney, sometimes pulling against the restraints, for a couple of minutes, according to the Associated Press news agency. That was followed by several minutes of heavy breathing until breathing was no longer perceptible.
In a final statement ahead of his execution, Smith said: “Tonight, Alabama causes humanity to take a step backwards. … I’m leaving with love, peace and light.”
Alabama Governor Kay Ivey said the execution was justice for the murder-for-hire killing of 45-year-old Elizabeth Sennett in March 1988.
“After more than 30 years and attempt after attempt to game the system, Mr Smith has answered for his horrendous crimes. … I pray that Elizabeth Sennett’s family can receive closure after all these years dealing with that great loss,” she said in a statement following Smith’s execution.
Sennett was found dead in her home with eight stab wounds in the chest and one on each side of her neck. Smith was one of two men convicted in the killing. The other, John Forrest Parker, was executed in 2010.
Prosecutors said the men were each paid $1,000 to kill Sennett on behalf of her pastor husband, who was deeply in debt and wanted to collect on the insurance. The husband, Charles Sennett Sr, killed himself when the investigation focused on him as a suspect, according to court documents.
Smith’s 1989 conviction was overturned, but he was convicted again in 1996. The jury recommended a life sentence by 11-1, but a judge overrode that and sentenced him to death.
Alabama no longer allows a judge to override a jury’s death penalty decision.
There were 24 executions in the United States in 2023, all of them carried out by lethal injection.