Mont. Code Ann. § 72-12-401

In a proceeding involving the probate, either contested or uncontested, of a will in which the signature of the testator or of any witness is an issue, any party to the proceeding may file with the court a verified petition requesting that the original be delivered to a handwriting expert residing and having a place of business outside the state or outside the county for an examination of any of the signatures on the will.