Definition and Explanation:

Amicus curiæ (Latin for friend of the court; plural amici curiæ) briefs are legal documents filed by non-litigants in appellate court cases, which include additional information or arguments that those outside parties wish to have considered in that particular case. Appellate cases are otherwise limited to the factual record and arguments coming from the lower court case under appeal, and so amicus curiæ briefs are a way to keep the possibly broad legal effects of court decisions from depending solely on the parties directly involved in the case. Non-profit legal advocacy organizations such as the American Civil Liberties Union frequently submit amicus curiæ briefs to advocate for or against a particular legal change or interpretation.

If a case may have effects on other parties, then they may file amicus curiæ briefs. For example, if a decision will affect an entire industry, even though it is brought up against only one company, other companies may file briefs as amici curiæ. Similarly, if a law in one state is under evaluation, and another state has a law that would be affected by the decision, then this other state may file a brief as an amicus curiæ.

Occasionally, however, amicus curiæ are not opinions on the argument or on one part of the argument, but simply an academic perspective. For example, if the law gives deference to a history of legislation of a certain topic, a historian may choose to evaluate the claim using his expertise. An economist, statistician, or sociologist may choose to do the same.

The court has discretion to grant or deny permission of parties to file briefs as amicus curiæ as it wishes. Generally, cases that are very controversial will attract a number of such briefs.

Legal Interpretations:

"... a phrase that literally means "friend of the court" -- someone who is not a party to the litigation, but who believes that the court's decision may affect its interest." William H. Rehnquist, The Supreme Court, page 89.

Rules Defining Use:

"An amicus curiae brief that brings to the attention of the Court relevant matter not already brought to its attention by the parties may be of considerable help to the Court. An amicus curiae brief that does not serve this purpose burdens the Court, and its filing is not favored." Rule 37(1), Rules of the Supreme Court of the U.S.

"FRAP 29. BRIEF OF AN AMICUS CURIAE A brief of an amicus curiae may be filed only if accompanied by written consent of all parties, or by leave of court granted on motion or at the request of the court, except that consent or leave shall not be required when the brief is presented by the United States or an officer or agency thereof, or by a State, Territory or Commonwealth. The brief may be conditionally filed with the motion for leave. A motion for leave shall identify the interest of the applicant and shall state the reasons why a brief of an amicus curiae is desirable. Save as all parties otherwise consent, any amicus curiae shall file its brief within the time allowed the party whose position as to affirmance or reversal the amicus brief will support unless the court for cause shown shall grant leave for a later filing, in which event it shall specify within what period an opposing party may answer. A motion of an amicus curiae to participate in the oral argument will be granted only for extraordinary reasons." Rule 29. Federal Rules of Appellate Procedure (FRAP).