Governor Mary Fallin signed bill allowing nitrogen execution into law . Chamber is pumped full of gas , and body dies from lack of oxygen . Method will become Oklahoma 's first choice after lethal injection . Supreme Court is due to rule on whether current execution drugs are legal . If gas execution is not available , state will use electric chair or firing squad .
Governor Mary Fallin signed bill allowing nitrogen execution into law . Chamber is pumped full of gas , and body dies from lack of oxygen . Method will become Oklahoma 's second choice after lethal injection . Supreme Court is due to rule on whether current execution drugs are legal . If gas execution is not available , state will use electric chair or firing squad .