The United States Patent and Trademark Office (the "PTO") is one of the oldest agencies in the American administrative system. Throughout the history of the United States Court of Appeals for the Federal Circuit ("Federal Circuit") and its predecessor courts, the factual decisions of the PTO administrative boards have been reviewed by the same standard that is applied to decisions of district courts. The standard that has been used is the "clearly erroneous" standard, and its use to review PTO decisions dates back over one hundred years.
Peter J. Corcoran III,
Administrative Procedure Act Standards Governing Judicial Review of Findings of Fact Made by the Patent and Trademark Office,
Rich. J.L. & Tech
Available at: https://scholarship.richmond.edu/jolt/vol7/iss1/3