What is prosecution history estoppel?

What is prosecution history estoppel?

Prosecution history estoppel is the principle that statements used in communications between a patent attorney and a patent Examiner at the USPTO can and will be used against an Applicant if a patent is litigated. Patent history estoppel can be used against an Applicant to disavow claim scope through the interpretation of limitations within claims.

During prosecution of a United States patent, an Examiner at the USPTO may issue office actions. In the office actions, the examiner may point out prior art that reads on the claims. Therefore, narrowing or clarifying amendments may be made to overcome the prior art. Under Festo (a famous patent case) , the Federal Circuit has held that narrowing claim amendments create a presumption that the patent application surrendered the territory between the originally filed claims and the amended claims. Accordingly, by narrowing the limitations of the claims, patent applications directly give up claim scope.

However, creating arguments in a response to an Examiner’s rejections in Office Actions can indirectly create prosecution history estoppel. If the arguments themselves in a response to an Office Action include limiting or “clarifying” arguments or reasoning may be construed in a limiting fashion, if the case is ever litigated.

Therefore, it is important when drafting responses to Office Actions to limit prosecution history estoppel while responding to Office Actions. The following are several ways to draft responses to Office Actions that limit prosecution history estoppel.

1)      Conduct inventor interviews. By conducting inventor interviews with Examiners at the USPTO prior to responding to an Office Action an Applicant can recite their arguments off the record during the interview. By verbally discussing arguments during a phone interview or in-person interview with the Examiner the arguments discussed during the interview will not be made of record detail, aside from those in the interview summaries.

2)      If you are responding to an Office Action with clarifying amendments it is beneficial to include a disclaimer in the arguments section, such as: “To expedite prosecution and without conceding to the Examiner’s positions, Applicant has amended independent claim 1 to recite, inter alia “…” By writing a disclaimer, Applicants at least make note that they are not admitting to the Examiner’s rejections, which could be later interpreted as an admission.

3)      When making clarifying amendments, in the arguments section of a response only quote to the limitations as recited in the claims, and do not include extra language in the response to clarify what the claims means. This is because the claims by themselves should stand on their own, by clarifying what the claims mean in extra words, these extra words create prosecution history estoppel that can be later used against you.

4)      When arguing against cited art, do not make arguments of how your claims are different than the cited art, make arguments of how the cited art is different than your claims. By characterizing the cited art instead of your claims you clarify the cited art, and do not make prosecution history estoppel of the meaning of your claims.