In inter partes review (IPR) proceedings, the PTAB will often uphold the validity of dependent claims despite finding the independent claim invalid. Dependent claims recite additional limitations that must be separately accounted for in the prior art references in the Petitioner’s asserted grounds. For assertions of obviousness in particular, a Petitioner’s invalidity arguments may align well with broader independent claims and some dependent claims, but may fall short where the limitations from certain dependent claims are not found or addressed. Importantly, a Petitioner cannot expect to remedy this in the Reply or in a request for rehearing. See, e.g., 3M Co. v. Evergreen Adhesives, Inc., No. 2020-1738, 2021 U.S. App. LEXIS 18956 (Fed. Cir. June 25, 2021) (non-precedential) (affirming the Board’s decision finding two dependent claims valid with limitations that were not separately addressed until a request for rehearing). This makes it incumbent on the Patent Owner to identify dependent claims that may stand alone and specifically address them in the Patent Owner Response (POR).

It goes without saying that dependent claims are narrower in scope by definition and harder to invalidate than the claims from which they depend. E.g., In re Tanaka, 640 F.3d 1246, 1250-51 (Fed. Cir. 2011). As such, they should not be overlooked in the POR or else the Patent Owner risks tethering their validity to broader claims with limitations more easily identified in the prior art. Importantly, the Board must provide a reason for upholding dependent claims where independent claims have been held invalid. In MaxLinear, Inc. v. CF CRESPE LLC, 880 F.3d 1373 (Fed. Cir. 2018), the Board’s decision to uphold the validity of the dependent claims at issue rested entirely on their conclusion that the independent claims were valid (a ruling which was later overturned due to collateral estoppel), and contained no separate analysis or discussion regarding the dependent clams. Id. at 1377. On appeal, the Federal Circuit found the independent claims invalid and remanded and instructed the Board to answer whether the dependent claims “present[ed] materially different issues that alter the question of patentability, making them patentably distinct from” the independent claims. Id. at 1378. But the Board has a limited basis to make this determination and cannot come up with reasons to invalidate any challenged claims on its own. This highlights the importance of using the POR to make a record of any “materially different issues” found with challenged dependent claims.

Dependent claims can carry the day and be used at trial even after the independent claims fall in an IPR. See, e.g., 3M Co., No. 2020-1738 (affirming the Board’s decision to reject Petitioner’s obviousness challenge to two dependent claims). This highlights the importance of defending those dependent claims, which may just be the last ones left standing at the end of the proceeding.