Most commonly used in U.S. law to describe a situation where the outcome of a court ruling is no longer of practical relevance, i.e., any ruling could no longer alter the facts. For example, a death penalty appeal is rendered moot by the defendant’s death, since the outcome of the case can no longer affect his fate. Where a case is “moot” a U.S. court may be unable to hear it because of the absence of any “case or controversy” as required by the U.S. Constitution.