Rule 806.Harmless Error

Rule 806 is one paragraph and it governs everything in Part VIII.

The rule

Unless justice requires otherwise, no error in admitting or excluding evidence, and no other error by the court or a party, is grounds for granting a new trial, setting aside a verdict, or vacating, modifying, or otherwise disturbing a judgment or order. At every stage the court must disregard all errors and defects that do not affect any party's substantial rights.

What it changes

Every ground in Rule 804 and Rule 805 runs through this filter. Establishing that something went wrong is not enough; the party must show the error affected a substantial right. An evidentiary ruling that excluded a document the court heard about from three other sources, an irregularity that changed nothing in the outcome, a defect in form — none supports disturbing the judgment.

The "unless justice requires otherwise" opening keeps discretion available, so the rule is not a mechanical bar.

Where it bites hardest in family cases

Two places. First, Rule 801(a)(7)'s clearly-erroneous standard already gives the trial court wide room on the facts; Rule 806 adds that even a legal misstep must have mattered.

Second, Rule 707's informal trial waives the Idaho Rules of Evidence outright. A party who consented to that waiver has no evidentiary error left to raise — Rule 806 would in any event require showing the admission changed the result.

Not a cure for everything

Rule 806 addresses error. It does not save a void judgment, which is independently attackable under Rule 805(b)(4), and it does not excuse a failure to make findings, which Rule 801(c) governs through its own motion requirement.