An appellate court or court of appeals hears cases that may legitimately warrant new decisions, according to the American Heritage New Dictionary of Cultural Literacy. Either party can bring a case to the court of appeals if the party is displeased with the decision of the original court and can demonstrate the legitimacy of the appeal.
A legitimate appeal usually occurs when new evidence arises or when the party is capable of posing a good argument that the original court misinterpreted the Constitution, the American Heritage New Dictionary of Cultural Literacy states. There are 12 federal courts of appeal, corresponding to 12 regionally distributed circuits that cover a number of states. A party is entitled to appeal a case at each level of appellate courts until the case reaches the United States Supreme Court.
According to the United States Courts website, a court of appeals hears not only appeals from lower courts in its circuit, but also appeals arising from federal administrative agency decisions. There are 94 judicial districts in the United States. The Court of Appeals for the Federal Circuit also hears cases that involve patent law or those cases decided by the Court of International Trade and the Court of Federal Claims.