A mistake in a court proceeding concerning a MATTER OF LAW or fact, which might provide a ground for a review of the judgment rendered in the proceeding.
The nature of the error dictates the availability of a legal remedy. Generally speaking, mistaken or erroneous application of law will void or reverse a judgment in the matter. Conversely, errors or mistakes in facts, upon which a judge or jury relied in rendering a judgment or verdict, may or may not warrant reversal, depending upon other factors involved in the error. However, appellate decisions make a distinction—not so much between fact and law, but rather, between harmless error and reversible error—in deciding whether to let stand or vitiate a judgment or verdict.
In litigation, a HARMLESS ERROR means that, despite its occurrence, the ultimate outcome of the case is not affected or changed, and the mistake is not prejudicial to the rights of the party who claimed that the error occurred. In other words, the party claiming error has failed to convince an appellate court that the outcome of the litigation would have been different if the error had not occurred. Most harmless errors are errors of fact, such as errors in dates, times, or inconsequential details to a factual scenario.
On the other hand, error that is deemed harmful in that it biased the ultimate decision of a jury or judge, constitutes reversible error, i.e., error that warrants reversal of a judgment (or modification, or retrial). A reversible error usually refers to the mistaken application of a law by a court, as where, for example, a court mistakenly assumes jurisdiction over a matter that another court has exclusive jurisdiction over. A court may erroneously apply laws and rules to admit (or deny the admission of) certain crucial evidence in a case, which may prove pivotal or dispositive to the outcome of the trial and warrant reversal of the judgment. Occasionally, a court may charge the jury with an instruction that applies the wrong law, or with an improper interpretation of the correct law. If the party claiming error can prove that the error was prejudicial to the outcome of the case or to the party's rights, the error will most likely be deemed reversible.
An example of potential harmful or reversible error of both law and fact might involve the age of a rape victim in a criminal trial for statutory rape, (where guilt is premised upon the actual age of the victim, and not on whether the sexual conduct was consensual).
In appellate practice, a party may not appeal an error that it induced a court to make (as by petitioning or moving the court to make a ruling which is actually erroneous). Appellate decisions refer to this as an invited error and will not permit a party to take advantage of the error by having the decision overruled or reversed.
The general use of the term error is often distinct from the use of the word mistake, especially in the law of contracts. In such cases, a MISTAKE OF LAW or fact (in the making of a contract, or performance thereupon) might result in a finding of harmless or reversible error, but the terms are not transitional.