The Role of Prosecution History (File Wrapper) in Patent Law

In patent litigation, most attorneys focus on the patent document itself. After all, the patent is being asserted in the litigation so it makes sense. But the patent document is not born in its final form. Rather, it starts as a patent application filed at the USPTO. The Examiner and applicant engage in the typical back and forth, each side making comments or amendments, and the final patent issues. As such, the iterative process is recorded. Per the MPEP 719, the electronic file record is the official record of all that transpired in that application. The patent file history (also known as the file wrapper) will contain all documentation related to the initial application, any cited prior art, all office actions and responses thereto, any interview summaries, search queries and results, the information disclosure statement, fee payments, etc. Accordingly, one can generally characterize the file history to contain two themes: (1) bureaucratic or administrative papers, and (2) substantive papers that shed light on the patent’s history and the invention. 

To this end, in patent litigation the substantive papers generally are more important than the administrative ones. This is because the office actions (e.g., rejections or objections) are the Examiner’s characterization of any issues, what the prior art may show, etc. The applicant’s responses thereto are designed to overcome those concerns. Claim amendments also show the pre- and post-amendment invention scope. In patent litigation, each party, jury, and the judges may resort to the “story” of the patent’s history to understand the patent. In this article we discuss a few areas where the patent story may matter: claim construction; doctrine of equivalents; inequitable conduct, and willful patent infringement. 

Role of Prosecution History in Claim Construction

Claim construction can play the pivotal role in patent litigation concerning infringement or invalidity. Under typical claim construction methodology, the prosecution history is part of the intrinsic evidence. Because claim construction can often be dispositive of the case, there are many rules involving claim construction methodology. One factor is to look at the prosecution history, but according to the 1996 Vitronics case, it may not be mandatory to look at it.  Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582 (Fed. Cir. 1996)(“Third, the court may also consider the prosecution history of the patent, if in evidence.”).

The file history may reveal what the Examiner thought certain claim terms may mean and what the applicant regarded as the claim meaning. Often times during prosecution, the applicant may characterize the prior art, its contents, and its applicability to the claims, and/or characterize a meaning for the claim term in order to secure allowance by overcoming the rejections. Yet in litigation later, the patentee may attempt to re-characterize a claim term to find infringement or avoid invalidity. The file history, therefore, can be used to corral what the patentee may say later in litigation based on what it said earlier. Conversely, it can reject what the challenger asserts as a claim term meaning. The prosecution history statements may imply what the applicant intended his claim to cover and hence what it was not intended to cover. This is often known as prosecution history disclaimer. See, Shashank Upadhye, Generic Pharmaceutical Patent & FDA Law, sect. 15:8 (2020 Ed.). Applicants should also take care in making statements in the file history because related patents can be impacted by what is said in lineage patents. That is, statements made in “upstream” prosecution histories apply to “downstream” patents.

Role of Prosecution History in the Doctrine of Equivalents

The Doctrine of Equivalents (DOE) is an alternate basis for determining direct, but non-literal infringement. There are two tests for the DOE: (1) the insubstantial differences test; and (2) the so-called function-way-result test. As with claim construction, the prosecution history may characterize the claim term at issue and may explain that claim terms role. To this end, the statements may help or hurt the patentees attempt to assert the DOE. The Supreme Court held that Prosecution History Estoppel (PHE) applies to narrow the scope of what the patentee can now say and that current arguments today cannot recapture that which was given away (or surrendered) during the application process. PHE can be: (1) amendment based estoppel or (2) argument based estoppel. For example in the pharmaceutical context, suppose an applicant (in the face of a prior art rejection) amends a claim to limit a formulation binder to be just HPMC. The accused infringer uses HPC, not HPMC. The Court may preclude DOE infringement because the amendment specifically narrowed the claim from all non-specific binders to the specific HPMC binder. The patentee is now estopped from asserting DOE that HPC is equivalent to HPMC. In another example, suppose the applicant claimed a binder but explained in office action responses that the binder in question was HPMC. The applicant further distinguished over prior art by arguing that the claimed binder was HPMC and that was not taught in the prior art. Though the Examiner did not require the final claim to recite HPMC as the binder specifically, the applicant’s statements may limit the term “binder” to mean a HPMC binder per argument based estoppel. 

Role of Prosecution History in Inequitable Conduct

Inequitable conduct is known as fraud on the patent office. It means that the patentee procured the patent by fraudulent means and its current enforcement would be improper. The proof of that fraud often comes from the prosecution history. One area is a statement made about the prior art in overcoming a rejection. The applicant may severely mischaracterize or outright lie about what the prior art teaches or doesn’t teach. While the Examiner may focus on a certain section of the prior art, the applicant may mischaracterize other parts of the art. In another area, data is often presented in life sciences patents. The data presented in the application may be false (or otherwise misleading) and the applicant may not tell the Examiner the whole story regarding the data. The data may be submitted in affidavits or other declarations that form part of the prosecution history. The submission may fail to show testing conditions, any conflict of interests, any negative data and cherry plucking positive data, etc. 

Other areas of potential inequitable conduct during the application process may also involve partial translations of prior art or burying material prior art in a long list of references cited in the IDS.

Role of Prosecution History to Show Knowledge of a Patent for Potential Willfulness

Another area of the prosecution history is in willful patent infringement not involving that patent. For example, suppose ABC is suing XYZ company on the ‘111 patent. ABC wants to show that XYZ’s patent infringement was willful because XYZ knew of ABC’s ‘111 patent. Aside from traditional notice rules, ABC may show knowledge of the patent through prosecution history. Particularly, suppose that XYZ itself has its own ‘888 patent in the same or similar technology area. During prosecution of XYZ’s ‘888 patent application, the Examiner cites to ABC’s ‘111 patent as prior art and fully explains the rejection of the ‘888 claims in view of the ‘111 patent. XYZ responds to the office action, discusses the ‘111 patent and why the rejection is overcome, and the ‘888 patent now issues. ABC may allege that XYZ was on notice of the ‘111 patent during the ‘888 prosecution. When it responded to the rejection, it knew or should have known about the claims in the ‘111 patent. It responded in earnest to the rejection. And it ought to have triggered some duty to investigate the scope of the ‘111 patent as applied to XYZ’s accused infringement. Of course, XYZ may argue that the ‘111 patent was cited for prior art purposes and that doesn’t trigger any duty to obtain a freedom to operate (FTO) opinion. One court upheld the jury finding that because the patent-in-suit was cited itself during the infringer’s own patent application process, that among other things put the infringer on notice of the patent. See, Honeywell Intern., Inc. v. Hamilton Sundstrand Corp., 166 F.Supp.2d 1008, 1037 (D. Del. 2001), affirmed in part, vacated in part on other grounds in Honeywell Intern. Inc. v. Hamilton Sundstrand Corp., 370 F.3d 1131 (Fed. Cir. 2004)(en banc). 

Therefore, there may be distinctions between whether a cited patent as prior art in the accused infringer’s own patent does or doesn’t put the defendant on notice for willfulness purposes. For example, if the Examiner simply cited the patent in a list of prior art cited, without more, then the infringer could argue that this not sufficient notice. If the Examiner cited to the patent as prior art and also fully explained it in the rejection, then the allegation of notice may be stronger. If the accused infringer itself cited the patent in an IDS, then a stronger argument exists that the infringer was on notice of it because he himself found the patent and submitted it. Willfulness requires a totality of the circumstances analysis and as such there are no hard and rigid rules. The facts matter. 

Practical Considerations

In patent law, the patent itself tends to garner the most attention. But as shown above, the story of the patent matters. We described above how statements made in the prosecution history can later shape the litigation. Patent applicants may not think about how each statement may impact the later litigation. Most patent applications do not get impacted with litigation. But when a patent is involved in litigation, each party will surely scrutinize the file history for any useful nuggets. While it may seem like overkill, patent applicants may need to “Mirandize” each submission before it’s filed. That is, an applicant must think about how a statement made can be used against him later on in court. Similarly, consistent with the estoppel laws, applicants should carefully explain the reasons for any amendment or argument. Applicants should be careful about characterizations of the prior art, reasons for amendments, etc. And while careful scrutiny of the response may increase costs for the client, given the unknown future impact, the increased cost may be worth it. 

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