In St. Pierre v. United States (1942), the U.S Supreme Court ruled that a case becomes moot if it loses its character as a present, live controversy of the kind that must exist for federal courts to have authority under Article III of the Constitution. The petitioner, Albert St. Pierre, was convicted and sentenced to jail for contempt after refusing to answer questions in front of a grand jury investigating alleged criminal activities in labor unions despite being granted immunity from prosecution based on his testimony. While his appeal was pending before the Supreme Court, he completed serving his sentence which led government attorneys arguing that since he had already served out his sentence, there is no longer any actual controversy; thus making it moot or irrelevant whether or not he should have been required to testify.

In the dissenting opinion for St. Pierre v. United States, Justice Frank Murphy argued that a case should not be considered moot simply because the sentence of imprisonment has been served and completed by the appellant. He believed that legal consequences could still arise from conviction, such as affecting one's reputation or being used against them in future cases, thus making it necessary to address whether or not there was an error in trial proceedings even after sentences have been served. Furthermore, he contended that if a court can only review criminal cases where punishment is ongoing then this would create an unfair situation where short-term sentences cannot be reviewed while long-term ones can be scrutinized thoroughly due to their duration.