Nitrogen gas executions: how it works and why it’s controversial

Kenneth Smith, who was executed by Alabama, appeared to convulse during procedure, as critics have likened it to human experimentation

Alabama has used a new method of execution: nitrogen gas.

Kenneth Smith, who survived the state's previous attempt to put him to death by lethal injection in 2022, was put to death Thursday by nitrogen hypoxia. It is the first new method of execution since lethal injection was introduced in 1982.