The standard of review is a shorthand description of the type of analysis that the appeals court applies to the decision being appealed. The concept of standard of review on appeal is somewhat similar to the concept of standard of proof in a trial. In a civil trial, the plaintiff must typically prove the elements of the cause of action by a preponderance of the evidence, whereas in a criminal trial, the prosecution must typically prove the elements of the crime beyond a reasonable doubt. “Preponderance of the evidence” and “beyond a reasonable doubt” are each standards of proof; beyond a reasonable doubt is a much more demanding standard than preponderance of the evidence. The factfinder (a jury, or the judge if there is no jury) applies the standard of proof to the evidence to determine the verdict.
On appeal, the appeals court applies the standard of review to the decision being appealed to determine whether to alter or affirm the decision. Depending on the type of decision being appealed, the appeals court provides more or less deference to the lower court’s decision. De novo review, the least deferential standard, gives no deference at all. On some issues, trial court judges have discretion, and appeals courts will not reverse decisions on those issues without an abuse of discretion, a more deferential standard. Appeals courts give great deference to lower courts on issues of fact. In civil cases, fact findings are typically subject to a highly deferential any evidence or clearly erroneous standard. In criminal cases, fact findings are subject to a rational trier of fact or sufficient evidence standard, which is also highly deferential but functions differently from the any evidence standard due to the requirement of proof beyond a reasonable doubt. Finally, small classes of trial court errors known as plain error are considered so clearly erroneous that they need not be objected to at trial.