Montana Title 46. Criminal Procedure § 46-11-205. Amending information as to substance or form

(1) The court may allow an information to be amended in matters of substance at any time, but not less than 5 days before trial, provided that a motion is filed in a timely manner, states the nature of the proposed amendment, and is accompanied by an affidavit stating facts that show the existence of probable cause to support the charge as amended. A copy of the proposed amended information must be included with the motion to amend the information.

(2) If the court grants leave to amend the information, the defendant must be arraigned on the amended information without unreasonable delay and must be given a reasonable period of time to prepare for trial on the amended information.

(3) The court may permit an information to be amended as to form at any time before a verdict or finding is issued if no additional or different offense is charged and if the substantial rights of the defendant are not prejudiced.