In law, an appeal is a process for requesting a formal change to an official decision.

The specific procedures for appealing, including even whether there is a right of appeal from a particular type of decision, can vary greatly from country to country. Even within a jurisdiction, the nature of an appeal can vary greatly depending on the type of case.

An appellate court is a court that hears cases on appeal from another court. Depending on the particular legal rules that apply to each circumstance, a party to a court case who is unhappy with the result might be able to challenge that result in an appellate court on specific grounds. These grounds typically could include errors of law, fact, or procedure (in the United States, due process).

In different jurisdictions, appellate courts are also called appeals courts, courts of appeals, superior courts, or supreme courts.

Who can appeal

A party who files an appeal is called an appellant or petitioner, and a party on the other side is called a respondent (in most common-law countries) or an appellee (in the United States). A cross-appeal is an appeal brought by the respondent. For example, suppose at trial the judge found for the plaintiff and ordered the defendant to pay $50,000. If the defendant files an appeal arguing that he should not have to pay any money, then the plaintiff might file a cross-appeal arguing that the defendant should have to pay $200,000 instead of $50,000.

The appellant is the party who, having lost part or all their claim in a lower court decision, is appealing to a higher court to have their case reconsidered. This is usually done on the basis that the lower court judge erred in the application of law, but it may also be possible to appeal on the basis of court misconduct, or that a finding of fact was entirely unreasonable to make on the evidence.

The appellant in the new case can be either the plaintiff (or claimant), defendant, or respondent (appellee) from the lower case, depending on who was the losing party. The winning party from the lower court, however, is now the respondent. In unusual cases the appellant can be the victor in the court below, but still appeal. For example, in Doyle v Olby (Ironmongers) Ltd 1 2 QB 158,

An appellee is the party to an appeal in which the lower court judgment was in its favor. The appellee is required to respond to the petition, oral arguments, and legal briefs of the appellant. In general, the appellee takes the procedural posture that the lower court's decision should be affirmed.

Ability to appeal

An appeal as of right is one that is guaranteed by statute or some underlying constitutional or legal principle. The appellate court cannot refuse to listen to the appeal. An appeal by leave or permission requires the appellant to move for leave to appeal; in such a situation either or both of the lower court and the appellate court may have the discretion to grant or refuse the appellant's demand to appeal the lower court's decision. A good example of this is the U.S. Supreme Court in which at least four justices must agree to hear the case if there is a constitutional issue.