Oklahoma has become the first U.S. state to approve the untested use of nitrogen gas for executions. A new law signed by Governor Mary Fallin establishes gas as a backup method if lethal injection drugs are unavailable, or if that method is blocked by a court. Nitrogen gas works by depriving the body of oxygen. It’s banned for use on animals in some states, and there is no record of it ever being used to execute humans. Executions remain on hold in Oklahoma as the Supreme Court considers its three-drug lethal injection method following the botched execution of Clayton Lockett, who took 43 minutes to die.