(1) A brief of an amicus curiae may be filed only after leave is granted by order of the supreme court on motion or when accompanied by written consent of all parties to the case. An amicus curiae shall file a brief within the time allowed to the party whose position the amicus will support, unless the court for good cause shown shall grant leave for a later filing. (2) When consent to the filing of an amicus curiae is refused by a party to the case, an original and 7 copies of a motion for leave to file may be presented to the court within the time allowed for the filing of the brief of the party to be supported. The motion shall concisely state the nature of the movant's interest, the facts or questions of law that have not been, or reasons for believing that they will not adequately be, presented by the parties, and their relevancy to the disposition of the case. A brief may be conditionally filed with the motion for leave. A party served with such motion may seasonably file an original and 7 copies of an objection concisely stating the reasons for withholding consent.
(3) Consent to the filing of a brief of an amicus curiae is unnecessary when the brief is presented for the State of New Hampshire by the attorney general (as amicus and not as a party); for any State agency authorized by law to appear on its own behalf by its appropriate legal counsel; or for any political subdivision of the State by its authorized law officer. (4) The court may on motion, in its discretion, permit an amicus curiae to be heard orally.