The question of the degree of deference that the Court of Appeals for the Federal Circuit should give to factual determinations by the Patent and Trademark Office came before the United States Supreme Court in the case of Dickinson v. Zurko. Traditionally, the Federal Circuit had used the same standard as used for reviewing court decisions when reviewing decisions of the PTO. The Administrative Procedure Act (5 USC 706) limits the right of a court when reviewing a decision of an agency to hold the agency's action unlawful on the basis of its incorrect finding of fact unless the decision was "unsupported by substantial evidence". The standard for an appellate court in reviewing the decision of a lower court is whether the lower court's decision is "clearly erroneous". The Commissioner argued that the Federal Circuit should give greater deference to findings of fact by the PTO by applying the standards for review set out in the Administrative Procedure Act.

The Supreme Court reversed a unanimous en banc decision of the Federal Circuit to agree with the Commissioner that since the PTO was a specialist tribunal, some deference should be paid to its fact-finding expertise. However, the Supreme Court commented that "(apart from the present case) we have failed to uncover a single instance in which a reviewing court conceded that use of one standard rather than the other would have produced a different outcome".