From 1981 to 1992 he served as the Chief of the Capital Punishment and Post-Conviction Litigation Division of the Alabama State Attorney General's Office. As the head of Alabama capital punishment unit, Carnes became, according to the National Law Journal, "the premier death penalty advocate in the country and a chief adviser on capital punishment to judges, the U.S. Justice Department and other prosecutors." Carnes re-wrote Alabama's death penalty statute, and defended its use before the Supreme Court of the United States on three occasions, including "Beck v. Alabama", 447 U.S. 625.