In modern judicial systems, most court judgments may be appealed to a higher court. After all, judges are not infallible, so let another court re-consider the pros and cons. In some cases a judgment rendered by the appeal court might still be appealed to a higher level court: this may happen in Hungary in criminal cases when the trial court and the appeal court rule differently. But surely at some point there will be no more possibilty for re-consideration of the merits of the case (guilt or innocence of the accused, a contracting party's obligation to pay, ownership of an estate established, or a marriage being void, whatever the litigation may be about) simply for the purposes of taking another look at the matter. (Res judicata accipitur.) 

Still even a case closed by final judgment, no matter if it was reached after or without appeal, may have to be re-opened if a new fact becomes known or a new proof becomes available. Most importantly, even in the absence of novum, there are legal procedures available to annul even a final judgment that is illegal (the sentence was pronounced by a clerk replacing the judge, the crime confessed was no longer a crime at the time of sentencing, the debtor's neighbor was ordered by the court to pay the debt, ownership was established in respect of an object that cannot be owned, to name some possibilities - no new fact, no new proof, just legal mistakes). If the legal system of a country, like that of Hungary,  is governed by a written constitution, then of the many possible illegalities that might conveivably affect a final judgment, perhaps the gravest although least obvious illegality is non-conformity with the country's written constitution. As written constitutions are necessarily expressed in very general terms (or they are "concise and vague" according to one statesman's wisdom of some years ago), a special forum may be established for the annulment of any final court judgment contrary to the constitution, and in fact for the annulment of any anti-constitutional legislation on which the final judgment was otherwise legally based: these are the powers of the Constitutional Court in Hungary. This body is not part of the ordinary judicial system of Hungary, its members are directly appointed by the legislature.

A constitutional complaint, asking for the annulment of a final judgment by reason of non-conformity with the constitution (the Basic Law of Hungary), can be lodged with the Constitutional Court within 60 days of the delivery of the final judgment. Legal representation is not compulsory, but admissibility for examination of the merits of the case has onerous prerequisites that may require argumentation based on legal theory, as cause-effect relationship needs to established between non-conformity with the Basic Law, or a question of fundamental importance of constitutional law needs to be formulated (Act CLX. of 2011. on the Constitutional Court).

It should also be kept in mind, that when a final court judgment violates a fundamental right that is protected both by Hungary's Basic Law and by the Convention for the Protection of Human Rights and Fundamental Freedoms, then according to present practice of the ECHR in Strasbourg, constitutional complaint in Hungary must be availed of before before lodging of an application with the ECHR.