Common law

In Anglo-American legal systems, a convicted defendant may move in the trial court to arrest judgment, or he may file a motion for a new trial. The legality of the conviction may also be challenged by appeal to a higher court. Criminal appeals were unknown in the traditional common law, but today they are universally granted by statute. In the United Kingdom, the Criminal Appeal Act of 1907 established an elaborate system of appellate procedure, proceeding from Magistrate’s Courts all the way to the House of Lords, the highest court of England until 2009, when it was replaced in that capacity by the Supreme Court. Extraordinary remedies available in English procedure include the writ of habeas corpus (determining the legality of holding the prisoner in custody) and the orders of mandamus (compelling an official to perform an act required by law), certiorari (requiring a lower court to present the trial record to a higher court), and prohibition (by which a higher court prohibits a lower court from exceeding its jurisdiction).

In the United States, a defendant convicted in a state or federal court can appeal to that state’s (or the appropriate federal) appellate court. Subject to certain restrictions, the defendant can turn to the federal court system when his rights under the U.S. Constitution have been violated in state court. Review by the U.S. Supreme Court is discretionary; the court grants it only in cases of general significance by issuing a writ of certiorari to the court whose judgment is to be reviewed. Even after the regular avenues of appeal are exhausted, defendants in custody can at any time apply for a writ of habeas corpus, challenging the prison warden’s right to keep the petitioner in custody and demanding his release. Since the warden’s right usually depends on the validity of the criminal judgment, habeas corpus constitutes an indirect method of review. Legislation in the 1970s curtailed access to federal courts on the basis of habeas corpus.

While defendants enjoy a liberal right to appellate review in criminal matters, the prosecution generally cannot appeal an acquittal. This is due to a strict interpretation of the concept of double jeopardy, which forbids that a defendant be tried twice for the same act.

Appellate courts do not take evidence but only decide points of law on the basis of the record. Since juries do not give reasons for their verdicts, appeals are usually based on allegations of faulty procedure (in particular, the admission and exclusion of evidence) and on erroneous statements on the applicable law in the judge’s instruction to the jury. The sentence is also subject to review in Britain and Canada but not in most of the United States.

Civil law

Appellate procedure on the Continent follows quite different rules. Most important, the prosecution as well as the defense can appeal a judgment, including the sentence. In some countries (e.g., Germany) it is possible to demand a new trial in a higher court if the original trial was held by a single judge. In other cases, appellate courts review only matters of substantive or procedural law, including the question of whether the lower court did everything necessary to find the relevant facts. Continental trial courts usually write elaborate reasons for their judgments, and it is these reasons that form the objects of the appellate courts’ scrutiny.

When appellate review is waived or exhausted, judgments are deemed final and can be executed. Final judgments can be overturned only if significant new evidence is found indicating that the decision was wrong.