1. Which standard of review applies to this argument?

The function of appeals in the American legal system is not to ensure that the trial court made no errors. Allowing appeals courts to review every decision made in the trial court, as part of a free-ranging search for errors, would prolong litigation and generate extraordinary costs. Therefore, federal courts have various procedural rules for what issues may be grounds for reversal. No appellate court will reverse any ruling if it finds only a harmless error. As defined by 28 U.S.C. § 2111, a harmless error or defect is one that does not affect the substantial rights of the parties.

Appellate courts use a different standard of review for pure questions of law and issues of fact. If the issue is a pure question of law, the appeals court typically reviews the issue de novo, which means no deference will be given to the trial court's ruling, and the appellate court will decide the issue from scratch. When the issue involves solely findings of fact and those facts were found by a jury, appellate courts are very reluctant to reverse. In federal court, the Re-examination Clause of the Seventh Amendment and Supreme Court case law hold federal courts to a very high standard for reversing a jury's findings. A federal appeals court will generally overturn a jury verdict because of what it perceives as a fact-finding error only if there is a complete absence of proof on some material issue.

Appellate courts apply a «clearly erroneous» standard when reviewing the fact-finding of a judge in a bench trial. Outlined in Federal Rule of Civil Procedure (FRCP) 52(a)(6), federal courts must not set aside findings of fact made from the bench unless those findings were clearly erroneous.

When reviewing discretionary rulings by the trial court, such as evidentiary or discovery rulings, appellate courts will use the abuse of discretion standard of review. The reviewing appellate court will be highly deferential to the trial court judge's factfinding ability.

A is correct. As explained above, discretionary rulings by the court, such as evidentiary rulings, are reviewed under the abuse of discretion standard of review, which is highly deferential. Here, a determination as to whether evidence is irrelevant or highly prejudicial and should be excluded is within the trial court's discretion because it requires an understanding of the entire case and the factual context in which the evidence is being offered. Therefore, it is reviewed on appeal using an abuse of discretion standard.

B is incorrect. An appellate court applies the clearly erroneous standard when reviewing findings of fact made by the trial court in a bench trial. This question specifically mentions a jury in the facts, so the case at the trial court level was not a bench trial. Therefore, the standard does not apply to judicial rulings on the admissibility of evidence in a jury trial.

C is incorrect. An appellate court applies the de novo standard to trial court rulings on pure issues of law. Because an evidentiary ruling involves the application of legal standards to facts—i.e., relevance and prejudice as related to the facts in the case—it is not a ruling on a pure issue of law and therefore not subject to de novo review.

D is incorrect. An appellate court applies the harmless error standard when it determines that a trial court's erroneous admission of evidence did not affect any party's substantial rights. It is a conclusion an appellate court reaches after reviewing and determining the impact of an erroneous evidentiary ruling, not the standard of review that the court applies to determine whether it was erroneous to admit the evidence in the first instance.