The best way to address errors in patent prosecution is to not make them. But what happens when mistakes inevitably occur?
This question was most directly answered in Hakim v. Cannon Avent, 479 F.3d 1313 (Fed. Cir. 2007). In that case, Hakim included the term “slit” in the claims of a parent application. During prosecution, Hakim also made arguments directed to the “slit.” The parent application eventually was allowed.
Hakim then filed a continuation application replacing the word “slit” with “opening.” Hakim also provided a letter to the USPTO explaining the claims were broadened. The Examiner subsequently allowed the continuation application without comment or rejection.
Ultimately, the Federal Circuit held the letter was insufficiently clear to inform the Examiner that the previous disclaimer of “slit” and the prior art avoided by the term “slit” may need to be revisited.
Hakim lost his case, but his actions were fairly laudable. More than thirteen years later, many (most?) practitioners still do not file letters in continuation applications indicating when the claims have been broadened.
Further, Hakim permitted the allowed parent application to become abandoned. This decision might have been quite strategic. Had Hakim allowed the parent application to issue, the Examiner likely would have rejected the child application on the ground of obviousness-type double patenting. Like many applicants, Hakim then might have filed a Terminal Disclaimer. However, filing a Terminal Disclaimer might have influenced the interpretation of the “opening.” E.g., Simpleair, Inc. v. Google LLC, 884 F.3d 1160, 68 (Fed. Cir. 2018) (concluding Terminal Disclaimers are relevant to meaning of child patent relative to parent).
I hope to revisit this topic in the future. For now, keep your disclaimer rescissions clear, and file letters with your continuation applications.