of counsel

a : a lawyer participating in the management or trial of a case in court …to have the assistance of counsel for his defense —U.S. Constitution amend. VI a right to counsel

b : a lawyer appointed or engaged to advise or represent a client in legal matters (as negotiations or the drafting of documents) — compare attorney

Note: A judge who has acted as counsel in a matter (as by advising an investigator) is disqualified from hearing the case.

: advise