Mont. Code Ann. § 46-14-205

If either the defendant or the prosecution wishes the defendant to be examined by a qualified psychiatrist, licensed clinical psychologist, or advanced practice registered nurse selected by the one proposing the examination in order to determine the defendant's fitness to proceed or whether the defendant had, at the time the offense was committed, a particular state of mind that is an essential element of the offense, the examiner must be permitted to have reasonable access to the defendant for the purpose of the examination.