Alabama has executed convicted a murderer Kenneth Eugene Smith with nitrogen gas, marking the first time the technique of execution has been utilized globally.
The state said the method would be humane, but critics called it cruel and experimental.
Officials said Kenneth Eugene Smith, 58, was pronounced dead at 8:25 p.m. at an Alabama prison after breathing pure nitrogen gas through a face mask to cause oxygen deprivation
Smith, lost two final challenges to the Supreme Court and one to a federal appeals court, contending that the execution was cruel and unusual.
The nitrogen gas execution marked 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.
Some doctors and organisations had expressed alarm about the method, and Smith’s attorneys asked the Supreme Court to halt the execution to review claims that it violates the constitutional ban on cruel and unusual punishment and deserved more legal scrutiny before it was used on a person.
Alabama and two other US states have approved the use of nitrogen hypoxia as an alternative method of execution because the drugs used in lethal injections have become more difficult to find, contributing to a fall in the use of the death penalty nationally.
