Prosecution History Disclaimer, and the Perils of Boilerplate Language
What you say to a patent examiner during prosecution can be used against you later, at least in some circumstances. One of the ways this can happen is through the doctrine of prosecution history disclaimer, where unretracted statements regarding interpretation of claim elements made during prosecution can be used to limit the scope of those elements in a later-issued patent.
A recent application of the doctrine can be found in a nonprecedential Federal Circuit opinion, Puradigm v. DRG Grp. Investments, No. 24-2299, (Fed. Cir. Apr. 1, 2026). The case involved an allegation of infringement of patent claims to photo-catalytic air purification cells. At issue was the meaning of “specular UV reflector” in the claims.
The district court found that the patentee (Puradigm) had limited the scope of the term during prosecution, and that accused-infringer DRG’s device did not have a “specular UV reflector” as so interpreted, and thus there was no infringement. Puradigm appealed.
In affirming the district court’s decision the Federal Circuit panel focused on two statements Puradigm made during prosecution. The first statement involved Bigelow, a prior art reference that the examiner had applied in rejecting broader versions of the claims than eventually issued. Of that reference Puradigm said, “Nowhere in Bigelow is anything regarding a specular reflector disclosed—either expressly or inherently.” DRG’s device had a reflective surface similar to that disclosed in Bigelow, and therefore Puradigm was found to have disclaimed the claim scope to cover such DRG’s reflective surface.
Puradigm argued against this finding, pointing out that the argument where it made the above-quoted statement did not convince the examiner, who then maintained the same rejection. It was only after Puradigm then added language to narrow the scope of the claim further did the examiner agree to allow the claims. Puradigm, by this line of reasoning, should not be found to have disclaimed claim scope by making an unsuccessful argument for patentability, later acquiescing to the examiner’s position by taking prosecution in a different direction, without repeating the earlier arguments.
This is where the second of Puradigm’s statements came into play. Of the various statements made by the examiner, Puradigm stated, “Applicant neither agrees nor disagrees with such statements and explicitly reserves the right to challenge such statements in the future should the need arise.” This statement was made twice, in the middle of identical boilerplate statements at the end of Office Action replies:
IV. FINAL MATTERS
The Office Action may make a number of statements regarding the pending claims, patent laws and regulations, prior art, and the state of the art that are moot in light of the amendments and/or remarks. The Applicant has not addressed all of such statements at this time. The Applicant neither agrees nor disagrees with such statements and explicitly reserves the right to challenge such statements in the future should the need arise. Furthermore, the Applicant does not concede that the references asserted in the Office Action qualify as prior art with respect to this application. For example, the Applicant reserves the right to antedate the alleged prior art reference(s) where applicable.
So even though the statement was boilerplate language, it had Puradigm explicitly saying that it “neither agrees nor disagrees” with the examiner’s position – hardly the stuff of an acquiescence. Furthermore, the statement regarding the Bigelow reference was related to the language subsequently added to the claims to secure allowance. Thus the district court’s finding of noninfringement was affirmed.
Note that had Puradigm expressly retracted its argument regarding the Bigelow reference, there probably would have been no finding of prosecution history disclaimer for the recited “specular UV reflector.” But that course of action has its own potential problems. As Prof. Dennis Crouch says in his Patently-O piece on the Puradigm case, “An explicit retraction is the textbook way to neutralize a prior narrowing statement. Of course, any retraction must be done carefully to avoid disrupting prosecution and to avoid creating further litigation minefields.”
The problem with Puradigm’s boilerplate language is that it explicitly avoids taking a position on the examiner’s statement, when the desirable default to avoid prosecution history disclaimer is to retract statements made in unsuccessful arguments for patentability. Perhaps some situation-specific boilerplate is called for in such a situation, such as the following:
Prior Arguments and Comments
Any unsuccessful arguments or comments made in response to previous rejection(s) should be considered retracted in view of the latest Action, unless the arguments or comments are explicitly made again by Applicant. Such retracted arguments or comments should not be considered as any sort of disclaimer of claim scope, as an admission regarding the scope of the claims and/or regarding the characterization of the prior art, or as constituting any sort of estoppel against Applicant.
In any event, in prosecuting a patent application one should always choose one’s words wisely, since (as noted at the beginning of this piece) what you say may be used against you later.
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