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When a patent drafter discloses but declines to claim subject matter, this action dedicates that unclaimed subject matter to the public. Application of the doctrine of equivalents to recapture subject matter deliberately left unclaimed would conflict with the primacy of the claims in defining the scope of the patentee's exclusive right.
Johnson and Johnston Associates (Johnston) asserted United States Patent No. 5,153,050 (the 050 patent) against R.E. Service Co. and Mark Frater (collectively RES). The 050 patent related to the manufacture of printed circuit boards. Without the invention claimed in the 050 patent, stacking by hand can damage or contaminate the fragile foil, causing discontinuities in the etched copper circuits. The invention adhered the fragile copper foil to a stiffer substrate sheet of aluminum. The specification of the patent read: “While aluminum is currently the preferred material for the substrate, other metals, such as stainless steel or nickel alloys may be used." A jury found that RES willfully infringed claims 1 and 2 of the patent under the doctrine of equivalents and awarded Johnston $ 1,138,764 in damages. Upon entry of judgment, the United States District Court for the Northern District of California further granted Johnston enhanced damages, attorney fees, and expenses. After a hearing before a three-judge panel on December 7, 1999, the United States Court of Appeals for the Federal Circuit ordered en banc rehearing of the doctrine of equivalents issue.
Could the doctrine of equivalents be used to hold RES liable for patent infringement?
The Court noted that Johnson’s 050 patent specifically limited the claims to a “sheet of aluminum” and the “aluminum sheet.” However, the specification of the patent read: “While aluminum is currently the preferred material for the substrate, other metals, such as stainless steel or nickel alloys may be used." Having disclosed without claiming the steel substrates, Johnston could not then invoke the doctrine of equivalents to extend its aluminum limitation to encompass steel. Thus, Johnston could not assert the doctrine of equivalents to cover the disclosed but unclaimed steel substrate. Accordingly, the court held that the district court erred as a matter of law in concluding that RES infringed the 050 patent under the doctrine of equivalents by using a steel substrate. Consequently, the appellate court reversed the district court’s judgment of infringement under the doctrine of equivalents.