Literally, friend of the court. A person with strong interest in or views on the subject matter of an action, but not a party to the action, may petition the court for permission to file a brief, ostensibly on behalf of a party but actually to suggest a rationale consistent with its own views. Such amicus curiae briefs are commonly filed in appeals concerning matters of a broad public interest; e.g., civil rights cases. They may be filed by private persons or the government. In appeals to the U.S. courts of appeals, an amicus brief 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.
An amicus curiae educates the court on points of law that are in doubt, gathers or organizes information, or raises awareness about some aspect of the case that the court might otherwise miss. The person is usually, but not necessarily, an attorney, and is usually not paid for her or his expertise. An amicus curiae must not be a party to the case, nor an attorney in the case, but must have some knowledge or perspective that makes her or his views valuable to the court.
The most common arena for amici curiae is in cases that are under appeal (are being reconsidered by the court) and where issues of public interest—such as social questions or civil liberties—are being debated. Cases that have drawn participation from amici curiae are those involving CIVIL RIGHTS (such as 1952's BROWN V. BOARD OF EDUCATION), CAPITAL PUNISHMENT, environmental protection, gender equality, infant ADOPTION, and AFFIRMATIVE ACTION. Amici curiae have also informed the court about narrower issues, such as the competency of a juror; or the correct procedure for completing a deed or will; or evidence that a case is collusive or fictitious—that is, that the parties are not being honest with the court about their reasons for being there.
The privilege that friends of the court are granted to express their views in a case is just that: amici curiae have no right to appear or to file briefs. Unless they represent the government, amici curiae must obtain leave (permission) to do so from the court, or consent of all parties in the case, before filing. No court is obligated to follow or even to consider the advice of an amicus curiae, even one it has invited.
The principle that guides the appropriate role of a friend of the court is that he or she should serve the court without also acting as "friend" to either of the parties. Rules of court and case law (past court decisions) have attempted to spell out the sometimes tricky specifics of how an amicus curiae should—and should not—participate in a case.
For example, Missouri's supreme court in 1969 distinguished the role of amicus curiae from the normal role of the attorney in assisting the court. In this case, the court requested the attorney who had formerly represented the parties in the case to help elicit testimony and cross-examine witnesses. The lawyer also made objections and argued objections against the city, which was defending the lawsuit over ZONING. In seeking the payment of attorney fees for his services, the attorney argued that he had served as amicus curiae due to his acting at the court's request. The supreme court found that "in the orderly and intelligent presentation of the case, he rendered assistance to the court, the same as any attorney who contributes to the orderly presentation of a case. He was appearing, however, not as an adviser to the court but as a representative of private litigants … advancing their partisan interests … and is not entitled to have the fee for his admittedly valuable and competent professional services taxed as costs" (Kansas City v. Kindle, 446 S.W. 2d 807 [Mo. 1969]).
The amicus curiae walks a fine line between providing added information and advancing the cause of one of the parties. For instance, she or he cannot raise issues that the parties themselves do not raise, since that is the task of the parties and their attorneys. If allowed by the court, amici curiae can file briefs (called briefs amicus curiae or amicus briefs), argue the case, and introduce evidence. However, they may not make most motions, file pleadings, or manage the case.
Whether participating by leave or by invitation, in an appearance or with a brief amicus curiae, a friend of the court is a resource person who has limited capacity to act.