Alabama has executed a man with nitrogen gas, putting him to death with a first-of-its-kind method that once again put the U.S. at the forefront of the debate over capital punishment. Officials said Kenneth Eugene Smith was pronounced dead at 8:25 p.m. Thursday at an Alabama prison. It marked the first time a new execution method has been used since lethal injection was introduced in 1982. The execution came after a last-minute legal battle in which Smith’s attorneys said the state was making him the test subject for an experimental execution method that could violate the constitutional ban on cruel and unusual punishment. Smith was one of two men convicted in the 1988 murder-for-hire slaying of Elizabeth Sennett, a pastor’s wife.