The attorney has the duties of the GAL. See Mont. Code Ann. § 72-5-315(2).
MRPC Rule 1.14" "(a) When a client's capacity to make adequately considered decisions in connection with a representation is diminished, whether because of minority, mental impairment or for some other reason, the lawyer shall, as far as reasonably possible, maintain a normal client-lawyer relationship with the client. (b) When the lawyer reasonably believes that the client has diminished capacity, is at risk of substantial physical, financial or other harm unless action is taken and cannot adequately act in the client's own interest, the lawyer may take reasonably necessary protective action, including consulting with individuals or entities that have the ability to take action to protect the client and, in appropriate cases, seeking the appointment of a guardian ad litem, conservator or guardian."
"Once the issue of incompetency is raised, it is the duty of the court to determine whether the party is competent and to appoint a guardian ad litem if the party is incompetent; absent that determination, an adjudication affecting the rights of the alleged incompetent cannot stand." State ex rel. Perman v. District Court of Thirteenth Judicial Dist., In and For Yellowstone Country, 690 P.2d 419 (Mont. 1984). "The following representatives may sue or defend on behalf of a minor or incompetent person: (A) a general guardian; (B) a committee; (C) a conservator; (D) a like fiduciary." M.R.Civ.P Rule 17. "A minor or an incompetent person who does not have a duly appointed representative may sue by a next friend, or by a guardian ad litem. The court must appoint a guardian ad litem--or issue another appropriate order--to protect a minor or incompetent person who is unrepresented in an action." M.R.Civ.P Rule 17.