When a lawful arrest is effected, a peace officer may reasonably search the person arrested and the area within such person's immediate presence for the purpose of: (1) protecting the officer from attack; (2) preventing the person from escaping; (3) discovering and seizing the fruits of the crime; or (4) discovering and seizing any persons, instruments, articles, or things which may have been used in the commission of or which may constitute evidence of the offense.
Scope Of Search Incident To Arrest
Mont. Code Ann. § 46-5-102, under Legality and Admissibility.
Mont. Code Ann. § 46-5-102