The American legal system relies heavily on precedent, prior court decisions that serve as authoritative rules in future similar cases. Under the doctrine of stare decisis, Latin for "to stand by things decided," courts generally follow precedents set by higher courts within the same jurisdiction, promoting consistency, predictability, and stability in the law. Although courts may overturn precedent in exceptional circumstances, the system of binding precedent is what makes the law a coherent body rather than a collection of disconnected rulings. An amicus curiae, or "friend of the court," brief may be filed by a non-party with a strong interest in a case's outcome to provide additional perspectives, information, or arguments to assist the court, especially in appellate and Supreme Court proceedings.
When a party believes the trial court made errors of law, that party may pursue an appeal, a legal proceeding in which a higher appellate court reviews the lower court's decision. The appellate court may remand the case by sending it back to a lower court for further proceedings, sometimes with instructions on how to apply the law correctly, and remand does not necessarily imply the original decision was wrong. At the highest level, the U.S. Supreme Court uses the writ of certiorari to select which cases to hear, an order directing a lower court to send up the record of a case for review, with the Court granting cert to roughly seventy to eighty cases per year. To bring a lawsuit in the first place, a plaintiff must establish standing by demonstrating injury in fact, causation, and redressability by a favorable court decision, ensuring the court addresses a genuine, live controversy.
Several doctrines limit repeated or improper litigation, conserving judicial resources and protecting parties from harassment. Res judicata, "a matter judged," prevents the relitigation of a case once a final judgment has been rendered, barring the same parties from bringing the same claims in a subsequent lawsuit. Double jeopardy, protected by the 5th Amendment, prohibits a person from being tried twice for the same offense after an acquittal or conviction, although under the dual sovereignty doctrine, separate sovereigns such as federal and state governments may each prosecute for the same conduct. A case becomes moot when the controversy is no longer active or the issues no longer live, generally precluding review, though exceptions exist for issues capable of repetition yet evading review. Estoppel is the legal principle preventing a person from asserting a position inconsistent with prior conduct on which another party reasonably relied, taking forms such as equitable, promissory, and collateral estoppel. Statutes of limitations set the maximum time after an event within which legal proceedings may be initiated, with limits varying by jurisdiction and the type of claim, after which the claim is generally barred.