Montana Title 46. Criminal Procedure § 46-11-301. Summoning grand jury

(1) A grand jury may only be drawn and summoned when the district judge, in the judge's discretion, considers a grand jury to be in the public interest and orders the grand jury to be drawn or summoned. The composition and drawing of a grand jury must be in accordance with the provisions of Title 3, chapter 15, part 6.

(2) The district judge may direct the selection of one or more alternate jurors, who shall sit as regular jurors before an indictment is found or a grand jury investigation is concluded. A member of the jury who becomes unable to perform the juror's duty may be replaced by an alternate.