Mont. Code Ann. § 72-2-114

An individual who fails to survive the decedent by 120 hours is deemed to have predeceased the decedent for purposes of homestead allowance, exempt property, and intestate succession, and the decedent's heirs are determined accordingly. If it is not established by clear and convincing evidence that an individual who would otherwise be an heir survived the decedent by 120 hours, it is deemed that the individual failed to survive for the required period. This section is not to be applied if its application would result in a taking of intestate estate by the state under 72-2-115.