Source: https://www.leechtishman.com/insights/blog/the-impact-of-festo-cases-on-the-doctrine-of-equivalents/
Timestamp: 2019-04-24 20:12:19+00:00

Document:
For more than a decade, the Supreme Court of the United States and the Court of Appeals for the Federal Circuit (“Federal Circuit”), in a series of cases entitled Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd, (“Festo” cases) discussed whether amendments made for a substantial reason related to patentability, including voluntary amendments not made in response to an Examiner’s rejection, preclude application of the doctrine of equivalents.
The Supreme Court and the Federal Circuit Court’s rulings in the “Festo” cases have steadily changed the parameters courts have used to determine the types of amendments made during the prosecution of a patent application that would later preclude the patentee from applying the doctrine of equivalents in a patent infringement litigation. Therefore, these rulings present some important issues regarding enforcement of patent rights of applicants of currently pending U.S. patent applications.
Doctrine of Equivalents (“DOE”): The purpose of the doctrine of equivalents is designed to protect patent holders by preventing a person from changing some immaterial details of an existing invention while maintaining the invention’s fundamental elements, in order to avoid liability for infringement of an existing invention. (See Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605, 608 (1950)).
However, there are also laws designed to protect the rights of the public to rely on the stated claims of the patent, which are publicly available through the United States Patent and Trademark (“USPTO”) website.
Prosecution History Estoppel (“PHE”): Prosecution history estoppel prevents a patent holder, in an infringement suit, from reclaiming “[a] subject matter surrendered during the course of proceedings in the Patent and Trademark Office.” (5A Chisum Section 18.05 (2)(D)). The purpose of PHE is to fairly notify the public as to the surrendered subject matter of a particular patent (i.e. a matter that is no longer claimed by the patent). Therefore, PHE precludes a patent holder from applying the DOE in enforcing its patent rights as to the subject matter it relinquished through an amendment during the course of proceedings in the Patent and Trademark Office.
Before the Supreme Court and the Federal Circuit Court modified and clarified the scope of PHE and DOE in “Festo” cases, the analysis as to whether PHE precluded the application of DOE primarily focused on whether an amendment to a patent application was made in order to overcome a specific rejection from an examiner based on lack of novelty or obviousness based on prior art requiring a specific amendment to an element or a language to which the examiner objected. (Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd., 535 U.S. 722, 723-735 (2002); Festo Corp., 344 F.3d 1359, 1384 (2003)).
As the Supreme Court clarified its holding regarding applicability of PHE in Warner-Jenkins by stating that “[s]imply because estoppel has been discussed most often in the context of amendments made to avoid the prior art, it does not follow that amendments made for other purposes will not give rise to estoppel.” (Festo, 535 U.S. 722 at 734).
In 1993, Festo Corporation sued Shoketsu Kinzoku Kogyo Kabushiki Co. (“SMC”) in the U.S. District Court for the District of Massachusetts alleging that SMC infringed two of its patents literally and under the doctrine of equivalents. Although the jury found that SMC’s product did not literally infringe Festo’s patents, it nevertheless infringed the patents under the doctrine of equivalents.
At the time one of Festo Corp.’s patent was pending before the USPTO, the patent examiner issued an Office Action requesting (per 35 U.S.C.A. §112) Festo Corporation to further clarify the invention. During the drafting of the amendments, Festo Corp. narrowed the claim thereby surrendering an element of the claimed invention.
The Federal Circuit Court and the Supreme Court cases determined that the amendment that Festo Corporation made in response to the Office Action was “voluntary” because the narrowing amendment that Festo Corporation made to the patent application was neither made in response to a specific rejection of a claim language by an examiner nor required by the examiner. In other words, the extent to which the Festo Corp’s amendment narrowed the claim in the application had the effect of surrendering the equivalents of certain subject matters. The Federal Circuit concluded that that Festo Corporation could have foreseeably drafted a broader claim language in clarifying the invention but where there is no reason for choosing to narrow the claim, the Federal Circuit agreed with the district court that Festo simply opted not to pursue such a broader claim. (Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 234 F.3d 558, 568 (Fed.Cir.2000); and Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., WL 1510657 at 19 (1993)).
The Supreme Court, in determining whether an estoppel applied to a voluntary amendment to preclude the application of DOE, looked to see whether a broader claim description was foreseeable at the time the amendment was made. (Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 740). The Court held that if the equivalent of the subject matter at issue in the litigation was disclosed in the field of the particular invention, then the broader claim description was foreseeable. Id. Therefore, if the applicant did not draft a broader claim language when the option to do so was foreseeable, the presumption that the applicant chose to not pursue the available broader claimed applied. Id.
The Supreme Court and Federal Circuit (in remand) held that PHE applies to the amendment that Festo corporation made to its claim and that PHE precluded the application of DOE in the lawsuit against SMC.
The years following the conclusion of the “Festo” appeals, Federal Circuit as well as various district courts have steadily applied the more flexible “foreseeability” test to determine whether prosecution history estoppel applied to “voluntary” amendments made to the patent claims to preclude the application of the doctrine of equivalents. (See for example, Duramed Pharmaceuticals v. Paddock Laboratories, Inc., 644 F.3d 1376, 1379 (2011). See also Monsanto Co. v. E.I. Dupont Nemours and Co., WL 3095539 (2012)).
In view of the foregoing, a patentee should actively engage in discussions with its attorney regarding any proposed amendments related to patentability of a pending application and prioritize which patent application(s) in its portfolio requires the investment of prosecuting with a heightened vigilance.
If you have any questions about the doctrine of equivalents or the “Festo” cases, please contact Esther J. Choe. Esther is an Associate in Leech Tishman’s Intellectual Property Practice Group. Esther is based in the firm’s Pasadena office and can be reached at 626.796.4000 or echoe@leechtishman.com.

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