“Amicus curiae”

Jurisdiction: United States United States

Latin for "friend of the court." It is advice formally offered to the court in a brief filed by an entity interested in, but not a party to, the case.

Source: United States Courts
Jurisdiction: New Zealand New Zealand

A person (usually a barrister) appearing in court who doesn't represent any of the parties to the case, and assists the court by pointing out matters of law (or fact) that have been overlooked, or presents opposing arguments so that both sides of a case can be heard. Literally the term means a 'friend of the court'.

Source: New Zealand Ministry of Justice