The Lost Precedent of the Reverse Doctrine of Equivalents

41 Pages Posted: 3 Oct 2015 Last revised: 7 Aug 2016

See all articles by Samuel Ernst

Samuel Ernst

Golden Gate University School of Law

Date Written: 2015


Proponents of legislative patent reform argue that the current patent system perversely impedes true innovation in the name of protecting a vast web of patented inventions, the majority of which are never even commercialized for the benefit of the public. Opponents of such legislation argue that comprehensive, prospective patent reform legislation would harm the incentive to innovate more than it would curb the vexatious practices of non-practicing entities. But while the “Innovation Act” wallows in Congress, there is a common law tool to protect innovation from the patent thicket lying right under our noses: the reverse doctrine of equivalents. Properly applied, this judge-made doctrine can be used to excuse infringement on a case-by-case basis if the court determines that the accused product is substantially superior to the patented invention, despite proof of literal infringement. Unfortunately, the reverse doctrine is disfavored by the Court of Appeals for the Federal Circuit and therefore rarely applied. It was not always so. This article is the first comprehensive study of published opinions applying the reverse doctrine of equivalents to excuse infringement between 1898, when the Supreme Court established the doctrine, and the 1982 creation of the Federal Circuit. This “lost precedent” reveals a flexible doctrine that takes into account the technological and commercial superiority of the accused product to any embodiment of the patented invention made by the patent-holder. An invigorated reverse doctrine of equivalents could therefore serve to protect true innovations from uncommercialized patents on a case-by-case basis, without the potential harm to the innovation incentive that prospective patent legislation might cause.

Keywords: patents, patent law, intellectual property, intellectual property law

Suggested Citation

Ernst, Samuel, The Lost Precedent of the Reverse Doctrine of Equivalents (2015). 18 Vanderbilt Journal of Entertainment & Technology Law 467 (2016), Chapman University, Fowler Law Research Paper No. 15-16, Available at SSRN:

Samuel Ernst (Contact Author)

Golden Gate University School of Law ( email )

536 Mission Street
San Francisco, CA 94105
United States


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