United Nations experts urged U.S. authorities on Wednesday to halt the planned execution of a prisoner by asphyxiation using pure nitrogen, saying the untested method may subject him to "cruel, inhuman or degrading treatment or even torture." It would be the first time a judicial execution has been carried out anywhere in the world using asphyxiation with an inert gas, according to capital-punishment experts. Smith, 58, is one of only two people alive in the U.S. to have survived an execution attempt after Alabama botched his previously scheduled execution by lethal injection in November 2022 when multiple attempts to insert an intravenous line failed. Smith's lawyers have said the untested gassing protocol likely violates the U.S. Constitution's ban on "cruel and unusual punishments", and have argued a second attempt to execute him by any method is unconstitutional. Spokespeople for Alabama Governor Kay Ivey and the U.S. State Department did not respond to questions about the U.N. experts' statement.