A prisoner in Alabama has become the first inmate in the world to be executed with nitrogen gas.
Convicted murderer Kenneth Smith, 58, was put to death after the US Supreme Court declined a legal bid to halt his sentence.
His official time of death was 8.25pm on Thursday (2.25am UK time).
According to witnesses, the execution took about 22 minutes and Smith appeared to remain conscious for several minutes.
For at least two minutes, he appeared to shake and writhe, sometimes pulling against the restraints. That was followed by several minutes of heavy breathing, until breathing was no longer perceptible.
State authorities had predicted unconsciousness within seconds and death within minutes.
In a final statement, Smith said: “Tonight Alabama causes humanity to take a step backwards… I’m leaving with love, peace and light.”
He made the ‘I love you sign’ toward his wife and other family members who were witnesses. “Thank you for supporting me. Love, love all of you,” Smith said.
The use of nitrogen gas is highly controversial and critics say it’s cruel and experimental. It had never been used before anywhere.
It involves clamping a mask tightly to the face, covering the mouth and nose.
The mask is then fed with nitrogen gas. The person continues to breathe normally, but with no oxygen present the body gradually shuts down until death occurs – effectively they are suffocated.
Reverend Jeff Hood, who witnessed the execution, said the reality did not match Alabama’s predictions of a quick death.
“We didn’t see somebody go unconscious in 30 seconds. What we saw was minutes of someone struggling for their life,” he said.
“Heaving back and forth, we saw spit, we saw all sorts of stuff develop from the mask. The mask was tied to the gurney, ripping his head back and forth over and over again.”