Ireland has a common law legal system with a written constitution that provides for a parliamentary democracy. The court system consists of the Supreme Court, the Court of Appeal, the High Court, the Circuit Court and the District Court, all of which apply the Irish law and hear both civil and criminal matters. Trials for serious offences must usually be held before a jury. The High Court, Court of Appeal and the Supreme Court have authority, by means of judicial review, to determine the compatibility of laws and activities of other institutions of the state with the constitution and the law. Except in exceptional circumstances, court hearings must occur in public.