State v. Hardground, 433 P.3d 711

Hardground was charged with Failure of Sexual Offender to Provide Notice of Change of Residence; the Information originally (and repeatedly) listed December 19, 2013 as the offense date but included later filings identifying earlier or different predicate convictions.
The Third Amended Information (filed pretrial) still reflected the December 19, 2013 date and identified a 1994 Northern Cheyenne Tribal Court sexual conviction as the registration predicate.
At trial on June 4, 2015, immediately before opening statements, the State orally moved to amend the Information to change the offense date to August 5, 2014, calling the change a typographical error and relying on earlier filings that referenced August 5, 2014.
Hardground objected, arguing the date alteration changed the proofs required and prejudiced his preparation because the registration statute imposes a strict 3-business-day reporting window tied to specific dates of residence change.
The District Court allowed the amendment; the jury convicted Hardground and he was sentenced to five years. The Supreme Court of Montana reversed, holding the late change to the alleged date was a substantive amendment and prejudiced the defendant.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether the district court abused its discretion by permitting the State to amend the Information on the day of trial to change the alleged offense date	State: the date change was a scrivener's error, an amendment of form, and did not prejudice Hardground	Hardground: changing the date altered the required proofs (the 3-day registration element) and prejudiced defense preparation; amendment should have complied with the 5-day-before-trial rule for substantive changes	The Court held the date change was a substantive amendment that altered the proofs and prejudiced Hardground; permitting the amendment that day was an abuse of discretion, so conviction reversed and remanded

State v. Wilson, 172 P.3d 1264 (Mont. 2007) (standard: abuse of discretion for amendments to charging documents)
State v. Yecovenko, 95 P.3d 145 (Mont. 2004) (date-range amendment held one of form when elements/proofs remain the same)
City of Red Lodge v. Kennedy, 46 P.3d 602 (Mont. 2002) (morning-of-trial amendment that added substantive allegations prejudiced defendant)
State v. Hallam, 575 P.2d 55 (Mont. 1978) (amendment changing offense subsection can be substantive)
State v. Romero, 926 P.2d 717 (Mont. 1996) (clarifying that when facts are set with certainty, correcting statutory references is permissible, but substantive factual changes are not)