Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co. — En Banc Federal Circuit Creates Complete Bar to Doctrine of Equivalents After Claim Amendment
The Federal Circuit sitting en banc adopted a sweeping complete-bar rule: any narrowing amendment made during prosecution to comply with the Patent Act creates an absolute estoppel that bars all claims of equivalence for the amended element — a rule later rejected by the Supreme Court in 2002.