Law a person who offers, or is called in, to advise a court on some legal matter
See amicus curiae in American Heritage Dictionary 4
(ə-mēˌkəs kyo͝orˈē-īˌ)
nounpl.a·mi·ci curiae(ə-mēˌkē)
A party that is not involved in a particular litigation but that is allowed by the court to advise it on a matter of law directly affecting the litigation.