The rules for post-grant proceedings established by the America Invents Act (AIA) provide that once the Patent Trial & Appeal Board (Board) renders a final written decision, a petitioner in an inter partes review (IPR) is prohibited from raising before the patent office, a district court, or the International Trade Commission “any ground that the petitioner raised or reasonably could have raised during that inter partes review.”1 Initially, many believed that such broad estoppel provisions would deter parties from considering such post-grant proceedings.

In this regard, there has been much uncertainty about how courts will apply the IPR estoppel provisions of 35 U.S.C. § 315(e)(1) and whether a petitioner will be estopped in a subsequent IPR from raising grounds deemed “redundant” (i.e., multiple, similar arguments challenging the patentability of the same claims within an IPR) in a previous IPR.2

The Board has established that, absent a showing that newly cited prior art was “unknown or unavailable” at the time of filing a first petition, “a reasonable inference that those references were known or available” can be made when considering a second petition.3 The Board has also stated in dicta that, “could have raised” includes “prior art which a skilled searcher conducting a diligent search would reasonably … have been expected to discover.”4 Those decisions emphasized the importance for petitioners to present their best art when filing an IPR petition.

A recent decision by the Board has shed some light on the matter.5 Petitioner filed a second IPR petition following an adverse final written decision in a first IPR that was also filed by Petitioner on the same patent. Using combinations of cumulative art, the first IPR petition raised seven grounds of unpatentability based on obviousness, but the proceeding was instituted under only one of those grounds on the basis that the others were redundant. In response to the second IPR petition, the Board determined that Petitioner was estopped under 35 U.S.C. § 315(e)(1) from raising a new ground for invalidity based on obviousness (Ground 2) because, at the time of the first IPR petition, Petitioner was aware of, and indeed cited, all the same prior art as Ground 2. As a result, the Board concluded that Petitioner reasonably could have raised Ground 2 during that proceeding and, having failed to do so, was prohibited from raising it in the second IPR petition.

Conversely, the Board determined that Petitioner was not estopped from raising one of the grounds (Ground 1) that was previously raised, but found redundant, in the first IPR petition. At issue was whether a petitioner is estopped in a second IPR petition from raising grounds of unpatentability that were also raised in a first IPR petition but not instituted in that proceeding because the Board found them redundant. The Board held that “[b]ecause the Board did not reach the merits of the challenge presented in Ground 1 when deciding whether to institute a trial in the [first] IPR, … Petitioner is not estopped from asserting Ground 1 in this proceeding.”6

Citing 37 C.F.R. § 42.2 and the Federal Circuit7, the Board relied on the distinction between the phases before and after an IPR is instituted (i.e., preliminary proceeding and trial, respectively) and noted that “the estoppel provisions of 35 U.S.C. § 315(e)(1) apply only to grounds that petitioner 'raised or reasonably could have raised during [the] inter partes review.'“8

The Board reasoned that “grounds raised during the preliminary proceeding, but not made part of the instituted trial, are not raised during an inter partes review and cannot be the basis for estoppel under 35 U.S.C. § 315(e)(1). Nor are such grounds ones that reasonably could have been raised during the review, because once denied, the Board's decision on institution prevents petitioner from raising that ground during trial.”9 The decision in this case is consistent with recent dicta from Judge Todd Hughes at the Federal Circuit who was quoted during oral argument stating that it would be “untenable” to estop petitioners from challenging validity on grounds deemed redundant.10

While these decisions highlight the importance of “getting it right” in the first IPR petition, they suggest that a subsequent bite at the apple may be available in a second IPR petition if not time-barred, and the Board finds that previously redundant grounds for invalidity can nevertheless establish a reasonable likelihood of prevailing. Moreover, the Central Reexamination Unit would not care whether the ground was “redundant,” and so it could permit a losing petitioner to file an ex parte reexamination request based on such a ground. Ultimately, it remains to be seen whether federal courts will agree with the Board's interpretation of the estoppel provisions.