PROSECUTION HISTORY ESTOPPEL (FILE-WRAPPER ESTOPPEL)

Author : Att. Önder Özden [1]

In this Article, we mainly aim to focus on the term so-called “Prosecution History Estoppel” basically for purposes of clarifying its significant role to be exploited as a defense tool against patent infringement claims specifically based on “doctrine of equivalents”. The rationale of this term has been incorporated in Turkish Industrial Property Code No.6769 under Article 89/6 and it is being exercised in patent infringement cases where the patent owner attempts to broaden the scope of patent claims despite the fact he/she has already narrowed down them during or after the prosecution of the patent application or where the patent owner makes contradictory comments or constructions that would resurrect subject matter previously surrendered during prosecution history of the patent application.

Given the above objective of this Article, we will not lay stress on or drill down any specific jurisprudence, patent legislation or academic research in respect of Turkish or foreign patent laws but will merely and simply emphasize on the said term’s rarely enjoyed (especially in Turkey) functionality and its scope of applicability in patent lawsuits.

The term “Estoppel” in patent law is a legal term meaning that a second argument is prohibited if it is inconsistent with a first argument. In a patent context, it bars an inventor from admitting something to the Patent Office and later contradicting that admission, whether before the Patent Office or before a court.

Traditionally, the doctrine of prosecution history estoppel has been defined as an equitable tool for determining the scope of patent claims. The doctrine bars the patentee from construing its claims in a way that would resurrect subject matter previously surrendered during prosecution of the patent application, and thus prevents a patentee from enforcing its claims against otherwise legally equivalent structures – in view of doctrine of equivalents- if those structures were excluded by claim limitations added to avoid prior art. The traditional view depending upon the nature and purpose of an amendment has been changed recently and all amendments made for the purpose of patentability are now deemed to have the effect of depriving the inventor of a claim interpretation that includes equivalent structures [2]

Respectively, both the doctrine of equivalents [3] and prosecution history estoppel play important roles in the determination of patent infringement. The prosecution history estoppel has a priority when there is a conflict between the applications of these two principles, because prosecution history estoppel is one of the factors that limit the application of the doctrine of equivalents [4]. A patentee may invoke the doctrine of equivalents to proceed against an alleged infringer if his or her device “performs substantially the same function in substantially the same way to obtain the same result.” The test is necessarily premised on the underlying assumption that each of the “elements” recited in the claim is found somewhere in the accused product or process.

Even if a claim is not literally infringed, a patent owner can still be protected by asserting the doctrine of equivalents, which “allows the patentee to claim those insubstantial alterations that were not captured in drafting the original patent claim but which could be created through trivial changes.” This doctrine was utilized “[t]o temper unsparing logic and prevent an infringer from stealing the benefit of the invention.” [5]

Although the doctrine of equivalents works in favor of patentees, protecting against potentially infringing inventions that do not fall within the literal language of the claim, there are limitations on the doctrine of equivalents. One of these limitations include prosecution history estoppel. As explained in the above paragraphs of this Article, prosecution history estoppel may bar the patentee from asserting the doctrine of equivalents if the scope of the claims has been narrowed by amendment during prosecution. When the patent examiner rejects a claim, the applicant is given the right to appeal the rejection. However, if the applicant chooses not to appeal, “a narrowing amendment made to satisfy any requirement of the Patent Act may give rise to an estoppel.” [6]

In this sense, adding new technical features into the independent claim -picking technical features from the specification and adding them into the independent claim or using a subordinate claim as a new independent claim- is a common manner of amendments in practice, and therefore leads to the change of the scope of the independent claim. If such a change produced an essential effect on the patent right, for example overcoming the lack of novelty or inventive step, then all of the other technical features other than the new added one should be excluded from the scope of the independent claim (i.e., the prosecution history estoppel should be applied) [7].

Having said that prosecution history estoppel mostly arises where (a) there is no literal infringement, (b) the patent owner asserts infringement by equivalents, (c) the accused infringer affirmatively asserts the defense of prosecution history estoppel prevents the patent holder from asserting the doctrine of equivalents on the basis that the relevant subject matter has been disclaimed to overcome the lack of novelty or inventive step during prosecution.

Prosecution history estoppel applies most frequently where a patent applicant amends or cancels claims rejected by the Patent Office as unpatentable based upon prior art [8]. Well-settled notion that prosecution history estoppel can occur in two ways: by making a narrowing amendment to the claim (amendment-based estoppel), or by surrendering claim scope through argument to the patent examiner (argument-based estoppel). Under amendment-based estoppel, a patentee’s decision to narrow claims through amendment may be presumed to be a general disclaimer of equivalents in the territory between the original claim and the amended claim. This presumption may be overcome if the rationale underlying the amendment may be no more than a tangential relation to the equivalent in question. Under argument-based estoppel, the issue turned on whether the prosecution history evinced a clear and unmistakable surrender of the subject matter of the patent [9].

“..Prosecution history estoppel (“PHE”) is a legal instrument that courts use to strike a balance between the notice function of patent claims and the expanded protection that results when the Doctrine of Equivalents (“DOE”) is applied. PHE serves to limit, and is available as a defense to, the DOE. In Warner-Jenkinson Co. v. Hilton Davis Chemical Co., the Supreme Court held that a patentee may be estopped from relying on the DOE to assert infringement of a claim if the patentee amended the claim to avoid prior art. In this way, PHE tempers the patentee’s ability to assert infringement under the DOE after disclaiming subject matter by narrowing the scope of a claim in order to secure the grant of a patent. The Warner-Jenkinson Court placed the burden on the patentee to demonstrate that the reason for an amendment was unrelated to patentability in order to maintain an infringement claim under the DOE. If the reason for a narrowing amendment is not apparent from the prosecution history, the Court applies a rebuttable presumption that the amendment was made for reasons related to patentability. If the patentee is unable to rebut the presumption with an appropriate reason for the amendment, then PHE bars the patentee from asserting infringement under the DOE. PHE allows the public to rely on a patent’s prosecution history, and the estoppel resulting from a narrowing amendment, to avoid infringement of an amended claim….” [10].

As can be seen from the above quotation, prosecution history estoppel attaches importance to the public interest and allows the public to rely on a patent’s prosecution history to avoid infringement of an amended claim and its legally equivalent structures.

Given the importance attached to public interest, prosecution history estoppel has been extended to amendments made for other purposes and to arguments made by the applicant during or after the prosecution of the patent application irrespective of the type of the patent lawsuit in which prosecution history estoppel is being brought forward. Therefore, it may also be relevant in cases where the patentee makes additional declarations to prove infringement after the grant of the patent that will contradict with the original claim language and narrow down its scope in favor the accused infringer.

As a conclusion, we are of the opinion that the term “prosecution history estoppel” plays a very significant role (which has not been acknowledged and enjoyed fully in Turkish patent litigation yet) in the course of claim analysis and arguments asserted by the accused party that will prove the non-infringement not only in patent infringement actions based on doctrine of equivalence but also in a case that would prove the patentee’s contradictory comments or constructions that would resurrect subject matter previously surrendered during prosecution history of the patent application in a way that would extend the scope of patent protection in favor of the patentee.

[1] Co-founder of Ozden & Guclu Legal, Specialized in IP Law, www.ozdenguclulegal.com.

[2] https://smithhopen.com/glossary/prosecution-history-estoppel/

[3]  Means the scope of a patent right not only includes the essential technical features, but also the technical features that equivalent to the essential technical features in substance.

[4]  Application of The Prosecution History Estoppel in Determination of Equivalent Infringement, HE YUANYUAN, Client Support/Marketing Support, Clarivate, Darts-ip, https://clarivate.com/darts-ip/blog/application-of-the-prosecution-history-estoppel-in-determination-of-equivalent-infringement/

[5]  Dependent Patent Claims and Prosecution History Estoppel: Weakening the Doctrine of Equivelants, Matthew Eggerding, 50 St. Louis U.L.J. (2005), page 263

[6]  Dependent Patent Claims and Prosecution History Estoppel: Weakening the Doctrine of Equivelants, Matthew Eggerding, 50 St. Louis U.L.J. (2005), page 265

[7]  Application of The Prosecution History Estoppel in Determination of Equivalent Infringement, HE YUANYUAN, Client Support/Marketing Support, Clarivate, Darts-ip, https://clarivate.com/darts-ip/blog/application-of-the-prosecution-history-estoppel-in-determination-of-equivalent-infringement/

[8]  Infringement, Doctrine of Equivalents and Prosecution History Estoppel, Sumesh Reddy, Nalsar Visiting Faculty

[9]  Doctrine of Equivalents: Prosecution History Estoppel Can Be Both Amendment and Argument-Based, McDermott Will & Emery, Amy Mahan, PhD

[10]  Exceptions To Prosecution History Estoppel Are Hardly A Dime A Dozen: An Analysis Of The Federal Circuit’s Application Of The Narrow Exceptions To Prosecution History Estoppel Twelve Years After Festo, Rachel C. Hughey1 & Lınhda Nguyen, Cybarıs®, An Intellectual Property Law Revıew, page 61-62