Whether a method-of-execution challenge requires comparing the proposed lethal injection protocol to known alternative methods under the Eighth Amendment

1. In a method-of-execution challenge based on the Eighth Amendment, does this Court’s jurisprudence require lower courts to assess the substantiality of the risk of pain associated with the state’s method by comparing it to the known, available alternative suggested by the prisoner-plaintiff? 2. In this challenge to Mississippi’s use of a chemical paralytic and potassium chloride in its lethal injection protocol, did the Court of Appeals err when it found that Petitioner failed to show that these drugs pose a substantial risk of harm without comparing Respondents’ method to the known, available alternative of a single lethal dose of pentobarbital, which undisputedly eliminates the risk of suffocation and internal burning, and is used by 10 executing states and the Federal government?