Opinion ID: 2008618
Heading Depth: 1
Heading Rank: 11

Heading: doctrine of equivalents and its limitations

Text: [5,6] A device may infringe on a patent either literally or under the doctrine of equivalents. [19] New Tek contends that had its patent not lapsed, the Orthman device would have infringed under the doctrine of equivalents. Under this judicially created doctrine, a product or process that does not literally infringe upon the express terms of a patent claim may nonetheless be found to infringe if there is `equivalence' between the elements of the accused product or process and the claimed elements of the patented invention. [20] As we noted in New Tek I, the doctrine of equivalents prevents a copyist from making unimportant and insubstantial changes and substitutions in a patent which, though adding nothing, would be enough to take the copied matter outside the claim. [21] In reaffirming the modern viability of the doctrine of equivalents as a means of establishing patent infringement, the U.S. Supreme Court, in Warner-Jenkinson Co. v. Hilton Davis Chemical Co., [22] recognized the danger that broad application of the doctrine would conflict ... with the definitional and public-notice functions of the statutory claiming requirement under federal patent law. The Court stated that [i]t is important to ensure that the application of the doctrine, even as to an individual element, is not allowed such broad play as to effectively eliminate that element in its entirety. [23] [7-11] The determination of infringement under the doctrine of equivalents is limited by two primary legal doctrines: (1) prosecution history estoppel and (2) the all-elements rule. [24] Prosecution history constitutes a public record of the patentee's representations concerning the scope and meaning of the claims, and competitors are entitled to rely on those representations when ascertaining the degree of lawful conduct, such as designing around the claimed invention. [25] Prosecution history estoppel, also known as `file wrapper estoppel.' is a defense to infringement under which a patent holder who amends a patent application has no claim of infringement on patent claims not made in the final patent. [26] The all-elements rule prevents application of the doctrine of equivalents if applying the doctrine would vitiate an entire claim limitation. [27] According to this rule, an accused product does not infringe unless it contains each limitation of the claim, either literally or by an equivalent. [28] Determination of both literal infringement and infringement under the doctrine of equivalents is a question of fact. [29] But the application of the legal limitations imposed by prosecution history estoppel and the all-elements rule is a question of law which an appellate court reviews de novo. [30]