Mont. Code § 3-15-402
The secretary of state shall select from the most recent list of all registered active electors, as defined in 13-1-101, and make a list of the names of all persons qualified to serve as trial jurors, as prescribed in part 3 of this chapter. On or before the second Monday of April of each year, the secretary of state shall deliver the list to the office of court administrator. The office of court administrator shall then combine the resulting list with the list submitted to the office of court administrator under 61-5-127, ensuring that a person's name does not appear on the combined list more than once. Each name appearing on the combined list must be assigned a number that must be placed opposite the name on the combined list and must be considered the number of the juror opposite whose name it appears. A person's name may not appear on a combined list for more than one court during a 1-year term.
§ 3-15-402, MCA