What Is an Amicus Brief? A Plain Guide to Friend of the Court Filings

When a major case reaches the Supreme Court of the United States, news reports often mention that dozens of outside groups have weighed in. Business associations, civil rights organizations, states, scholars and former officials file their own written arguments, even though none of them is suing anyone. These filings are called amicus briefs, and they are a regular part of how American appellate courts work.

What the Term Means and Who Files

Amicus curiae is Latin for "friend of the court." An amicus is a person or organization that is not a party to the lawsuit but has a strong interest in how it is decided or has expertise that may help the judges. The plural is amici curiae, which is why news stories sometimes refer to "the amici."

An amicus brief is the written document that friend files. It is not evidence, and the amicus does not win or lose anything directly. Instead, the brief offers arguments, background or perspective that the parties themselves may not provide.

Common filers include the federal government, state attorneys general, trade groups, labor unions, advocacy organizations, professional associations, law professors and former officials. The Solicitor General, who represents the United States before the Supreme Court, often files in cases where the government is not a party. The Court sometimes formally invites those views, a practice lawyers call a "CVSG," short for a call for the views of the Solicitor General.

Why Courts Accept Them

Appellate judges decide questions that can affect far more people than the two sides in the courtroom. A ruling on a contract dispute, a regulation or a constitutional right can reshape an entire industry or community. Amicus briefs help judges see those wider effects.

Good amicus briefs avoid repeating what the parties already said. They might explain how a rule works in practice in a particular field, summarize research, describe how other states have handled the issue or flag consequences the parties overlooked.

History shows they can matter. In Mapp v. Ohio in 1961, the question the Court ultimately decided, whether evidence from an illegal search must be excluded in state courts, was pressed most directly by an amicus brief from the American Civil Liberties Union rather than by the main arguments of the parties.

The Filing Rules in Federal Courts

The Supreme Court's Rule 37 governs amicus filings there. Since an amendment that took effect in January 2023, a would be amicus generally no longer needs the consent of the parties or permission from the Court to file. The brief must still follow strict formatting, length and timing requirements.

Rule 37 also requires disclosure. An amicus must state whether counsel for a party wrote the brief in whole or in part and identify anyone, other than the amicus, its members or its lawyers, who paid for preparing or submitting it. The purpose is transparency, so the justices know whose voice they are really hearing.

In the federal courts of appeals, Federal Rule of Appellate Procedure 29 sets the framework. The United States, its officers and agencies, and states may file without asking. Other filers generally need the consent of all parties or permission from the court. The brief is usually limited to half the length allowed for a party's principal brief, and a court may strike an amicus brief that would force a judge to step aside. State courts and individual circuits add their own local rules.

Limits and Criticism

Amicus briefs are not without critics. Some observers worry that well funded groups can flood the Court with coordinated filings, or that briefs sometimes introduce factual claims that were never tested at trial. Judges are aware of these concerns and give each brief only the weight it earns.

An amicus also cannot expand the case. Courts generally decide the questions the parties raised, and a friend of the court usually cannot add new claims or ask for relief of its own.

Why It Matters to Ordinary People

Amicus briefs are one of the few ways people outside a lawsuit can be heard before a ruling that may affect them. When you read that a hospital association, a group of veterans or a coalition of states has filed in a major case, you are seeing the system invite broader input on questions that reach well beyond the courtroom.

This article is general information and not legal advice. Anyone considering an amicus filing should consult a lawyer familiar with the rules of the specific court, and Court Magazine will keep explaining the legal terms that shape the headlines.