interlocutory appeal – An interlocutory appeal, in the law of civil procedure is an appeal of a ruling by a trial court that is made before the trial itself has concluded. Most jurisdictions generally prohibit such appeals, requiring parties to wait until the trial has concluded before they challenge any of the decisions made by the judge during that trial. However, many jurisdictions make an exception for decisions that are particularly prejudicial to the rights of one of the parties. For example, if a party is asserting some form of immunity from suit, or is claiming that the court completely lacks personal jurisdiction over them, then it is recognized that being forced to wait for the conclusion of the trial would violate their right not to be subjected to a trial at all.

The Supreme Court of the United States delineated the law of interlocutory appeals for United States federal courts in the case of Lauro Lines s.r.l. v. Chasser et al., 490 U.S. 495 (1989), holding that under the relevant statute (28 U.S.C. § 1292) such an appeal would be permitted only if:

  • the outcome of the case would be conclusively determined by the issue
  • the matter appealed was collateral to the merits; and
  • the matter was effectively unreviewable if immediate appeal was not allowed.