article_snippet.sent: Oklahoma introduced a law allowing Oklahoma to use nitrogen gas to kill death row prisoners if lethal injections aren't available.
article_snippet.sent: Governor Mary Fallin signed into law a bill approving nitrogen as an alternative method of death, giving Oklahoma four different ways to enact Oklahoma death penalty.
article_snippet.sent: Oklahoma Oklahoma has legalized killing death row in-mates with nitrogen.
article_snippet.sent: Nitrogen - which has never been used to execute humans before - is now Oklahoma's second choice.
highlights_snippet.sent: Governor Mary Fallin signed bill allowing nitrogen execution into law .
  