best method. In April 2015, Governor Mary Fallin of Oklahoma signed a bill allowing nitrogen asphyxiation as an alternative execution method. Three years later, in March 2018, Oklahoma announced that, due to the difficulty in procuring lethal injection drugs, nitrogen gas will be used to carry out executions. After making "good progress" in designing a nitrogen execution protocol, but not actually carrying out any executions, Oklahoma announced in February 2020 it had found a new reliable source of lethal injection drugs, but would continue working on nitrogen execution as a contingency method. In March 2018, Alabama became the third state (after Oklahoma and Mississippi), to authorize the use of nitrogen asphyxiation as a method of execution. In the case Bucklew v. Precythe'', decided 1 April 2019, the U.S. Supreme Court ruled that a Missouri death row inmate could not avoid death by lethal injection and choose inert gas asphyxiation using nitrogen, since it has never been used in any execution in the world. See also Notes External links NIOSH respirator fact sheet U.S. Chemical Safety and Hazard Investigation Board Restraint asphyxia The Welfare of Birds at Slaughter: Humane Society of the United States comparison of controlled-atmosphere killing (CAK) to electrical water-bath stunning Controlled Atmosphere Killing: People for the Ethical Treatment of Animals Nitrogen Induced Hypoxia as a Form of Capital Punishment, by Michael P. Copeland, J.D., Thom Parr, M.S., and Christine Pappas, J.D., Ph.D. Execution by Nitrogen Hypoxia: Search for Scientific Consensus, by Kevin M. Morrow, J.D. Animal welfare Causes of death Execution methods Meat industry Nitrogen Poultry farming Slaughter methods Toxicology Asphyxia