Iura novit curia is a legal principle that is most commonly applied in civil law proceedings. A Latin phrase, iura novit curia specifically means that "the court understands or knows the law." As such, the plaintiff and the defendant in civil proceedings where this principle is applied only present the facts of the case and do not try to argue or prove the law that applies to the case. In accordance with iura novit curia, the judge will hear the facts and the pleadings of the litigants and make a ruling based on his own knowledge of the applicable laws. This practice is in keeping with the idea that the purpose for a civil proceeding is to ascertain the relevant facts, to investigate and ask questions, and then to determine which law applies to the case.
Illustrative examples of the principle of iura novit curia are the television courts, in which civil litigants forego their court cases and appear before the television judge. The litigants all take a turn to state the facts that support their cases. None of the litigants cite case law or argue the legal merits of their cases. After the judge has heard enough to make a decision, she renders a judgment on the case, unhindered by any limitations posed by the arguments of the litigants.
In theory, iura novit curia enables a court to make decisions according to the law even when one of the litigants has not broached an issue that justifies the judge's decision. For example, if a plaintiff sues a defendant for a breach of contract involving one aspect of the contract but fails to sue over another issue that has also been breached, the judge, if aware of both breaches, may base her decision on both breaches. Most jurisdictions, however, restrict their judgments to the claims made and remedies sought by the plaintiffs. For example, if a plaintiff sues a defendant for $300,000 US Dollars (USD), the judge will limit the award he orders to the $300,000 USD even though he may feel personally that the plaintiff deserves more.
In criminal law, the advocates for each party give the facts and also discuss the legal merits of the case. The judge rules exclusively on the basis of the attorney submissions. For example, if the prosecutor fails to present a piece of evidence in court, the judge may not use that evidence, even if he is aware of it, to guide his decision on the case. Additionally, if the prosecutor charges the defendant with a lesser crime in order to make a plea agreement, the judge does not render a sentence appropriate for a felony. In such cases, iura novit curia gives way to the principle of audiatur et altera pars, a party's privilege to be heard.