In United States law, a harmless error is a ruling by a trial judge that, although mistaken, does not meet the burden for a losing party to reverse the original decision of the trier of fact on appeal, or to warrant a new trial.
"[1]) The general burden when arguing that evidence was improperly excluded or included is to show that the proper ruling by the trial judge may have, on the balance of probabilities, resulted in the opposite determination of fact.
Federal Rule of Criminal Procedure 52(a) provides that "Any error, defect, irregularity or variance which does not affect substantial rights shall be disregarded."
In the Philippines, the harmless error rule is found in Section 6, Rule 51 of the 1997 Rules of Civil Procedure relating to appeals before the Court of Appeals: "No error in either the admission or the exclusion of evidence and no error or defect in any ruling or order or in anything done or omitted by the trial court or by any of the parties is ground for granting a new trial or for setting aside, modifying, or otherwise disturbing a judgment or order, unless refusal to take such action appears to the court inconsistent with substantial justice.
The court at every stage of the proceeding must disregard any error or defect which does not affect the substantial rights of the parties."