Mont. Code Ann. § 45-5-708
45-5-708 Past sexual behavior of victim
45-5-708 . Past sexual behavior of victim. In a prosecution for an offense under 45-5-702 , 45-5-703 , 45-5-705 , 45-5-706 , or 45-5-711 or a civil action under 27-1-755 , evidence concerning a specific instance of the victim's past sexual behavior or reputation or opinion evidence of the victim's past sexual behavior is inadmissible unless the evidence is admitted in accordance with 45-5-511 (2) or offered by the prosecution to prove a pattern of human trafficking by the defendant.