Documents to be used at a criminal trial or containing exculpatory evidence must only be provided on request, not proactively. There is a criminal procedure statute in Montana that fleshes out the details.
Federal Rule of Criminal Procedure 16, linked in the question, is the rule that applies in a U.S. District Court criminal case, but there is a parallel statute that applies in Montana's limited jurisdiction courts, with different numbering. The Federal Rules of Criminal Procedure do not apply in state courts.
Montana's Rules of Criminal Procedure (which apply to Justice Courts as well as all other state courts in Montana) can be found here, although there are also often local rules in each court. The prosecution's duty to disclose is set forth at Montana Statutes § 46-16-322 (rather than by a court rule as is the case in the federal system). It states:
Disclosure by prosecution.
(1) Upon request, the prosecutor shall make available to the defendant
for examination and reproduction the following material and
information within the prosecutor's possession or control:
(a) the names, addresses, and statements of all persons whom the
prosecutor may call as witnesses in the case in chief;
(b) all written or oral statements of the defendant and of any person
who will be tried with the defendant;
(c) all written reports or statements of experts who have personally
examined the defendant or any evidence in the particular case,
together with the results of physical examinations, scientific tests,
experiments, or comparisons;
(d) all papers, documents, photographs, or tangible objects that the
prosecutor may use at trial or that were obtained from or purportedly
belong to the defendant; and
(e) all material or information that tends to mitigate or negate the
defendant's guilt as to the offense charged or that would tend to
reduce the defendant's potential sentence.
(2) At the same time, the prosecutor shall inform the defendant of,
and make available to the defendant for examination and reproduction,
any written or recorded material or information within the
prosecutor's control regarding:
(a) whether there has been any electronic surveillance of any
conversations to which the defendant was a party;
(b) whether an investigative subpoena has been executed in connection
with the case; and
(c) whether the case has involved an informant and, if so, the
informant's identity if the defendant is entitled to know either or
both of these facts under Rule 502 of the Montana Rules of Evidence
and 46-15-324(3).
(3) The prosecutor may impose reasonable conditions, including an
appropriate stipulation concerning chain of custody, to protect
physical evidence produced under subsection (1)(d).
(4) The prosecutor's obligation of disclosure extends to material and
information in the possession or control of members of the
prosecutor's staff and of any other persons who have participated in
the investigation or evaluation of the case.
(5) Upon motion showing that the defendant has substantial need in the
preparation of the case for additional material or information not
otherwise provided for and that the defendant is unable, without undue
hardship, to obtain the substantial equivalent by other means, the
court, in its discretion, may order any person to make it available to
the defendant. The court may, upon the request of any person affected
by the order, vacate or modify the order if compliance would be
unreasonable or oppressive. The prosecutor may not be required to
prepare or disclose summaries of witnesses' testimony.
(6) The prosecutor shall furnish to the defendant no later than 5 days
before trial or at a later time as the court may for good cause
permit, together with their statements, a list of the names and
addresses of all persons whom the prosecutor intends to call as
rebuttal witnesses to evidence of good character or the defenses of
alibi, compulsion, entrapment, justifiable use of force, or mistaken
identity or the defense that the defendant did not have a particular
state of mind that is an element of the offense charged.
There is also a statutory duty of continuing disclosure if new evidence is generated after the disclosure is made by the prosecution. Montana Statutes § 46-15-327.
Are there instances where a county attorney can legally refuse to
provide documents?
Not all documents in the county attorney's office's possession have to be provided. For example, it can keep secret information about a confidential informant if that confidential informant will not be a witness at trial. But court rules generally require pre-trial disclosure of any documents that will be used at trial.
In Montana, Montana Statutes § 46-15-324 sets forth what need not be disclosed:
Materials not subject to disclosure.
(1) Except as provided in this section, disclosure is not required for
the superseded notes or work product of the prosecuting or defense
attorney.
(2) If exculpatory information is contained in the superseded notes or
work product of the prosecution, that information must be disclosed.
(3) Disclosure of the existence of an informant or the identity of an
informant who will not be called to testify is not required if:
(a) disclosure would result in substantial risk to the informant or to
the informant's operational effectiveness; and
(b) the failure to disclose will not infringe the constitutional
rights of the accused.
The other thing that doesn't have to be disclosed is the prosecutions's work product, e.g. outlines of questions to ask witnesses, or in house legal analysis, unless it refers to exculpatory evidence that has not otherwise been disclosed.
Is this an instance of where the 6th Amendment Confrontation clause
applies?
The 6th Amendment Confrontation clause is a constitutional parallel to the hearsay rule of evidence. There is a constitutional requirement that exculpatory evidence be provided by the prosecution upon request, but that flows from the due process clause and not the confrontation clause.
There is not a constitutional requirement to provide all incriminating evidence prior to trial, although it is often required by court rules or state law.
Footnote
Representing yourself in a criminal case, even a misdemeanor case, is beyond foolish. You should never attempt to do so yourself even if it is expensive to hire an attorney because you are not eligible for a public defender since you are not indigent.
You don't know what you don't know. The consequences of that ignorance can be serious.
