An amicus curiae, Latin for “friend of the court,” is a person or organization that is not a party to a case but is permitted to provide information, legal argument, or a broader perspective that may assist the court.

Pronounced uh-MEE-kus KYUR-ee-eye. The plural is amici curiae.

An amicus does not become a party by filing a brief. It ordinarily cannot control the litigation, settle the case, introduce evidence as a party would, or appeal simply because it participated as an amicus.

What an Amicus Brief Does

An amicus brief may help a court by:

• explaining the wider legal or practical effects of a decision;
• providing technical, historical, industry, or governmental context;
• identifying authorities or arguments the parties did not fully develop;
• describing how a rule operates in other settings; or
• addressing institutional interests affected by the case.

The most useful brief adds something relevant rather than repeating a party’s argument. The court is not required to follow an amicus position.

Amicus participation is governed by the rules of the court where the case is pending.

Who May File?

Federal Rule of Appellate Procedure 29 allows the United States, its officer or agency, or a state to file an amicus brief without the parties’ consent or leave of court.

Other proposed amici generally may file:

• with the consent of all parties, which the brief must state; or
• with the court’s leave.

A motion for leave must identify the proposed amicus’s interest and explain why the brief is desirable and why the matters asserted are relevant to the disposition of the case.

Supreme Court, state-court, and local appellate rules have their own filing requirements.

Disclosure and Independence

Federal appellate rules require an amicus brief to disclose specified information about:

• whether a party’s counsel authored the brief in whole or part;
• whether a party or its counsel contributed money intended to fund the brief; and
• other people who contributed funding intended for the brief.

Some government amici are excepted from the funding disclosure requirement.

These disclosures help the court evaluate the brief’s sponsorship and independence. “Friend of the court” does not require neutrality in the everyday sense; an amicus may support a party’s position while remaining a nonparty.

Timing and Form

Under Federal Rule of Appellate Procedure 29(a)(6), an amicus supporting a party is generally due no later than seven days after that party’s principal brief is filed, unless the court orders otherwise. Federal Rule 29 also governs covers, contents, length, service, and filing.

An amicus should check:

• the current rules of the specific court;
• whether consent or a motion is required;
• the filing deadline;
• word or page limits;
• disclosure requirements;
• electronic-filing and service rules; and
• whether the court has issued a case-specific order.

An untimely or noncompliant brief may be rejected.

Oral Argument

Filing an amicus brief does not provide an automatic right to speak at oral argument. Under Federal Rule of Appellate Procedure 29(a)(8), an amicus may participate in oral argument only with the court’s permission, which is discretionary.

Amicus, Amicus Brief, and Intervenor

• An amicus curiae is a nonparty who may offer information or argument to assist the court.
• An amicus brief is the written filing an amicus submits.
• An intervenor seeks to enter an existing action. In federal civil cases, Federal Rule of Civil Procedure 24 governs intervention: “On timely motion, the court must permit anyone to intervene who” meets the rule’s conditions, and “On timely motion, the court may permit anyone to intervene who” meets the conditions for permissive intervention.

Amicus Curiae Example

Suppose an appellate case concerns whether a new privacy rule applies to a technical system used across an industry. The parties focus on their own dispute. A professional association seeks leave to file an amicus brief explaining the system’s operation and the practical consequences of competing interpretations.

The association remains a nonparty. The court may accept the brief if it is relevant and useful, reject it if it merely duplicates party arguments, and decide the case without adopting the association’s position.

Key Takeaways

• An amicus curiae is a nonparty who offers information or argument to assist the court.
• An amicus brief does not confer ordinary party rights.
• Government entities have special federal appellate filing authority.
• Other amici generally need consent or leave of court.
• Authorship and funding disclosures promote transparency.
• Oral argument requires the court’s permission.
• Court-specific rules control timing, form, and participation.

Related term: Brief.

This glossary entry provides general information. Anyone considering an amicus filing should consult the current rules and orders of the particular court.