Amicus typically relates to the phrase amicus curiae (plural: amici curiae) which means “friend of the court.” Amicus is an individual or organization that is not a party to an action but who volunteers or is court-invited to advise on a matter before the court.
In the United States, amici curiae commonly file amicus briefs with courts at the appeals stage, though it is possible to file an amicus brief in federal district court. Amici may support a party or write neutrally in their briefs. Amici advise and assist courts on matters of law. Amici bring to the court’s attention certain matters of law that may have escaped court’s or parties’ consideration. An amicus’ role is limited to advising, they may not participate in the litigation as a party or an attorney to a party.
There are state and federal laws that govern the participation of an amicus curiae. For example, Rule 37 of the Rules of the Supreme Court of the United States and Rule 29 of the Federal Rules of Appellate Procedure specify the content, timing, and manner in which an amicus may participate in a proceeding.
[Last updated in May of 2020 by the Wex Definitions Team]