In Samsung Electronics America, Inc. v. Prisua Engineering Corp., the Fed. Cir. confirmed that, outside of the context of a motion to amend, the PTAB cannot cancel claims for indefiniteness in an IPR proceeding. Specifically, the Court found that if the PTAB cannot ascertain the scope of a claim with reasonable certainty for purposes of assessing patentability, the proper course for the PTAB to follow "is to decline to institute the IPR or, if the indefiniteness issue affects only certain claims, to conclude that it could not reach a decision on the merits with respect to whether petitioner had established the unpatentability of those claims under sections 102 or103. It would not be proper for the Board to cancel claims on a ground that is unavailable in an IPR."

In reaching this conclusion, the panel was also clear to explain (in a footnote) that "in cases in which the Board cannot reach a final decision as to the patentability of certain claims because it cannot ascertain the scope of those claims with reasonable certainty, the petitioner would not be estopped by 35 U.S.C. § 315(e) from challenging those claims under sections 102 or 103 in other proceedings."

This footnote is important because, in this case, the indefinite claims were originally excluded from trial pre-SAS but, post-SAS, were looped into the proceeding. With these claims now proceeding to a final written decision, the PTAB held, expectedly, that Samsung failed to establish that claims 1–4 and 8 of Prisua's U.S. Patent No. 8,650,591 were unpatentable under any of the asserted grounds. And this is where the Fed. Cir. faulted the PTAB—rather than finding that Samsung failed to carry their burden (possibly triggering estoppel), the Fed. Cir. explained that the PTAB should not have addressed these claims in their final written decision.

Thus, going forward, the PTAB appears to have two paths: (1) deny institution because the potentially indefinite claim term precludes review (e.g., if found in the sole independent claim) or (2) ignore the indefinite claim—although challenged by the petitioner—and proceed to a final written decision that will not substantively address the potentially indefinite claim, nor trigger estoppel.

For petitioners, this decision provides some security that a potentially indefinite claim term—especially if found in a dependent claim—will not undermine an entire IPR petition post-SAS. And in this regard, some petitioners may even choose to attack the indefiniteness of a dependent claim term in their IPR and argue that if the PTAB agrees, the IPR should nonetheless be instituted without reaching a decision on the merits as to this claim.

However, if the potentially indefinite term is found in an independent claim, particularly the only independent claim, petitioners still need to balance the strength of their litigation-indefiniteness position versus their unpatentability arguments. That is, by applying prior art to the term without mention of indefiniteness or language suggesting variability or ambiguity in the term's scope, the petitioners' IPR arguments may later be used to undermine an invalidity attack based on indefiniteness. Nonetheless, given the difficulty of prevailing on an indefiniteness argument during district-court litigation, it will generally be a rare case where a party believes that their indefiniteness arguments are so strong that they should consider foregoing IPR altogether.

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