Undue influence consists of: (1) the use by one in whom a confidence is reposed by another person or who holds a real or apparent authority over the other person of the confidence or authority for the purpose of obtaining an unfair advantage over the other person; (2) taking an unfair advantage of another person's weakness of mind; or (3) taking a grossly oppressive and unfair advantage of another person's necessities or distress.
What Constitutes Undue Influence
Mont. Code Ann. § 28-2-407, under Circumstances Which Affect Validity of Apparent Consent.
Mont. Code Ann. § 28-2-407