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
Group VII: Judgment · Last amended March 1, 2017 · Last verified July 14, 2026
In one sentenceRule 61 tells courts to overlook errors that didn't affect a party's substantial rights instead of ordering a new trial or disturbing a judgment over them.
Full Text of Rule 61
Amendment History
Added February 2, 2017, effective March 1, 2017.
Plain-English Summary
Trials are rarely flawless. A judge might admit a piece of evidence that should have been kept out, or exclude something that should have come in, or make some other misstep along the way. Rule 61 tells the court not to treat every stumble as a reason to start over. Unless the mistake affected a party’s substantial rights, the court is supposed to look past it — not grant a new trial, not set aside a verdict, and not vacate or modify a judgment because of it.
The rule applies at every stage of a case, and it doesn’t matter whether the error came from the judge or from one of the parties. The question is always the same: did the mistake change the outcome or unfairly hurt someone’s case? If not, the judgment stands. This is often called the harmless-error rule, and it exists so that lawsuits get decided on their merits instead of being retried over slips that made no real difference.
Frequently Asked Questions
What is a "harmless error" under Rule 61?
It is a mistake made during a case — admitting evidence that should have been excluded, for example — that did not affect a party’s substantial rights. Rule 61 says the court should disregard this kind of error rather than upset the judgment because of it.
Can a mistake in admitting or excluding evidence still lead to a new trial?
Yes, if the mistake affected a party’s substantial rights and justice requires a remedy. Rule 61 only bars relief for errors that made no real difference to the outcome.
Who decides whether an error affected a party’s substantial rights?
The trial court makes that call in the first instance, weighing whether the mistake likely changed the result or unfairly prejudiced a party’s case.
Does Rule 61 apply only to mistakes made by the judge?
No. The rule covers any error by the court or by a party, so long as it did not affect a party’s substantial rights.
How does Rule 61 relate to an appeal?
Rule 61 states the same harmless-error principle that appellate courts apply when reviewing a trial court’s rulings, so an error that would not justify relief in the trial court typically will not justify reversal on appeal either.
Source & verification. Rule text and amendment history are
reproduced verbatim from the Wyoming Rules of Civil Procedure, adopted by the
Supreme Court of Wyoming. Last verified July 14, 2026. ·
Official source
Also known as: harmless error ruleharmless error standardsubstantial rights errorevidentiary error appeal