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Patent prosecution is an iterative procedure in which the applicant frequently alters the language of their submitted claims. A patent’s prosecution history (i.e., the proceedings between the patent applicant and the USPTO from application filing to patent issuance) is relevant in the context of claim construction (for example, before a district court, the PTAB in a post-grant proceeding, or in the eyes of a third party analyzing the patent for freedom to operate reasons), as well as an assessment of infringement under the doctrine of equivalents. Both the idea of equivalents and the doctrine of prosecution history estoppel are relevant in determining patent infringement. This blog discusses prosecution history estoppel and its use in a doctrine of equivalents analysis.
What prosecution history estoppel does?
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. But before that, it is necessary to estimate whether the prosecution history estoppel can be applied in the determination of equivalent infringement. During the patent prosecution or invalidity procedures, applicants or patentees usually make amendments on claims or make statements that limit and narrow the scopes of claims in order to accommodate the patent law. 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. It was once believed that 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).
Applicability of Prosecution history estoppel
Patent prosecution is an iterative procedure in which the applicant frequently alters the language of their submitted claims. A patent’s prosecution history (i.e., the proceedings between the patent applicant and the USPTO from application filing to patent issuance) is relevant in the context of claim construction (for example, before a district court, the PTAB in a post-grant proceeding, or in the eyes of a third party analysing the patent for freedom to operate reasons), as well as an assessment of infringement under the doctrine of equivalents. Both the idea of equivalents and the doctrine of prosecution history estoppel are relevant in determining patent infringement. This is known as “classical” prosecution history estoppel, as determined in Hughes Aircraft Co. v. United States, 717 F.2d 1351, 1362. (Fed. Cir. 1983). Similarly, in Hilgraeve Corp. v. McAfee Assoc., Inc., 224 F.3d 1349 (Fed. Cir. 2000), it was determined that an applicant cannot change the claims in response to an examiner’s denial and then utilize the theory of equivalents to gain the same subject matter that was given up to obtain the patent.
Estoppel can also be established through arguments and representations submitted to the USPTO in order to receive the grant of a patent, even without a claim revision. This is where the border blurs the most, with claim construction standing out. Unmistakable declarations to the USPTO in favour of patentability, whether or whether they were necessary to win acceptance of the claims, will prevent the patentee from receiving protection for the subject matter relinquished under the theory of equivalents.In Caterpillar Tractor Co. v. Berco, S.p.A., 714 F.2d 1110, 1116 (Fed. Cir. 1983), the Federal Circuit noted that assertions made to foreign patent offices may also be considered for establishing the application of prosecution history estoppel. Representations to foreign patent offices should be taken into account where they contain relevant evidence.” When a court considers comments made in a foreign prosecution:
- The statement was made in an official procedure in which the patentee had every incentive to be careful in describing the scope of its invention;
- the patents are related and/or contain an identical claim; and the remark had nothing to do with distinctive elements of foreign patent law.
Prosecution history estoppel based on arguments and amendments to a single claim may be used to limit the reach of later claims in the same invention as well as in adjacent patents. Prosecution history estoppel, on the other hand, may not apply to patents granted previous to the behaviour that gave rise to the estoppel. (For instance, see Water Tech. Corp. v.Calco, Ltd., 850 F.2d 660, 667.) 1988 (Fed. Cir.).
The case of Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co. 535 US 722, 731-32 (2002) established the doctrine’s applicability. The notion of prosecution history estoppel, as decided in Festo, can be described as follows:
- every restricting change made to fulfil the requirements of the Patent Act may give rise to an estoppel;
- an unexplained narrowing amendment is presumed to have been made to satisfy the requirements of the Patent Act;
- an estoppel does not create an absolute bar to the application of the doctrine of equivalents;
- The applicant is presumed to have surrendered the scope of protection between the claim before amendment and after amendment;
- it is the applicant’s burden to show that the particular equivalent in question was not surrendered.
Pharma Tech Solutions, Inc. v. LifeScan, Inc., Case No. 19-1163 (Fed. Cir. Nov. 22, 2019) (Stoll, J).
The Federal Circuit noted that prosecution history estoppel can occur in two ways: by making a narrowing modification to the claim (amendment-based estoppel) or by relinquishing claim breadth via argument to the patent examiner (argument-based estoppel). In this case, the Court determined that Pharma was estopped on both amendment-based and argument-based estoppel.
A patentee’s choice to restrict claims through amendment may be interpreted as a broad disclaimer of equivalents in the region between the original claim and the revised claim under amendment-based estoppel. This assumption can be overcome if the justification for the modification has only a tangential relationship to the equivalent in question. In this case, Pharma voluntarily relinquished any bioelectrical blood glucose monitoring equipment that did not transform a number of current readings into analyte concentration measurements and compare the resultant analyte values. The Federal Circuit determined that this change was not incidental to the equivalent in question since the inventors clearly separated their innovation from the previous art using these converting and comparing limits.
The question under argument-based estoppel was whether the prosecution history demonstrated a clear and unambiguous surrender of systems that did not convert and compare analyte concentration readings. Based on this legal basis, the Federal Circuit determined that the inventors plainly and unequivocally separated their invention from previous art by imposing these constraints.
As a result, the Federal Circuit maintained the district court’s finding of both amendment-based and argument-based estoppel and granted summary judgment.
To summarize, while the concept of equivalents can be used to demonstrate infringement, prosecution estoppel may preclude such an argument because it applies to both direct infringement and infringement under the doctrine of equivalents. The Doctrine of Equivalents allows patent owners to safeguard their intellectual property in a different way, whether through Federal Court patent infringement lawsuits or International Trade Commission exclusion processes. The Festo judgment by the Supreme Court is a pivotal ruling that will have a significant impact on patent law adjudication. It specifies the conditions under which prosecution history estoppel should apply, and it introduces a new set of standards, the foreseeability, tangential connection, and reasonableness tests, to control the interplay between the theory of equivalents and prosecution history estoppel. However, the Festo tests reduce the breadth of the concept of equivalents compared to the “flexible bar” approach, and the responsibility is more on the patent prosecution to construct better claims for maximal protection.
Author: Anuja Saraswat – a student of B.A.LL.B (Hons.) from NMIMS Kirit P. Mehta School of Law (Mumbai), in case of any queries please contact/write back to us via email firstname.lastname@example.org or contact us at IIPRD.