Unless justice requires otherwise, no error in admitting or
excluding evidence -- or any other error by the court or a party -- is ground for granting a
new trial, for setting aside a verdict, or for vacating, modifying, or otherwise disturbing a
judgment or order. At every stage of the proceeding, the court must disregard all errors and
defects that do not affect any party’s substantial rights.
Rule 61.Harmless Error
Enacted effective October 1, 2011 · Last verified June 26, 2026
In one sentenceRule 61 is the harmless-error rule: a court must disregard any error — in admitting or excluding evidence or otherwise — that does not affect a party's substantial rights, and such an error is not grounds for a new trial or to disturb a judgment.
Full Text of Rule 61
Plain-English Summary
Not every mistake in a trial matters. Rule 61 directs that, unless justice requires otherwise, no error — in admitting or excluding evidence, or any other error by the court or a party — is grounds for a new trial, for setting aside a verdict, or for disturbing a judgment or order. At every stage, the court must disregard errors and defects that do not affect any party's substantial rights.
Frequently Asked Questions
What is the harmless-error rule?
It means a court will not grant a new trial or disturb a judgment because of an error — in an evidence ruling or otherwise — unless that error affected a party's substantial rights.
Source & verification. Reproduced verbatim from the Montana Code Annotated as
published by the State Law Library of Montana and the Montana Legislature. This rule has not been amended since its adoption.
Adopted by the Supreme Court of Montana (AF 07-0157). Last verified June 26, 2026. ·
Official text
Also known as: harmless error