Mont. Code Ann. § 5-5-417
Proceedings on failure to appear
5-5-417 . Proceedings on failure to appear. If the defendant does not appear, the senate, upon proof of service or publication as provided in 5-5-414 and 5-5-415 , may of its own motion or for cause shown assign another day for hearing the impeachment or may proceed in the absence of the defendant to trial and judgment.