Doctrine of Equivalents: Scope & Limitations

314-329The scope of a patent is not limited to its literal terms, but instead embraces all equivalents to claims described in a patent application. Limiting the scope of a patent to its literal elements, would allow a competitor to make an unimportant or insubstantial change to the patented invention and thereby defeat the patent. The doctrine of equivalents is an important tool of law (developed by the courts of United States) to determine infringement in cases of non-literal infringement. The doctrine removes unfairness that could result from an overemphasis on the literal language of patent claims, and thereby affords protection accorded to the patent. The doctrine strikes a balance between a fair scope for the patent and the notice the patent provides for the public, along with a balance between incentives to innovate and costs of uncertainty. This paper analyses the scope of the doctrine in the light of the different tests and legal bars, developed by courts. The paper also comments upon the problems associated with the doctrine and the significant changes brought about to it, by the landmark judgment of the Supreme Court of United States in Festo Corp v Shokestsu Kinzoku Kogyo Kabushiki Co