The US Patent & Trademark Office (PTO) terminated a pending ex parte reexamination after finding that the challenger was estopped because the prior art references could have been raised in a prior inter partes review (IPR). In re Tyler, Reexam. No. 90/014,950 (PTO Nov. 15, 2022).

In 2017, GITS Manufacturing filed two IPR petitions against a patent owned by G.W. Lisk after Lisk asserted the patent against GITS in district court. In 2018, the Patent Trial & Appeal Board issued final written decisions in each IPR, finding some claims unpatentable and maintaining the patentability of other claims. The Federal Circuit affirmed both IPR decisions in 2021.

In February 2022, the PTO initiated an ex parte reexamination of one of the patents based on a request filed by GITS. The reexamination proposed multiple grounds of unpatentability based on four prior art references that were not involved in the IPRs. GITS included a lengthy discussion and an expert declaration describing the prior art searches GITS performed in support of the certification that it was not estopped under 35 U.S.C. § 315(e)(l) from asserting the grounds in the reexamination. Lisk filed a petition to vacate the reexamination proceeding, alleging that GITS was estopped because the reexamination references reasonably could have been raised in the previous IPRs. Lisk’s petition was supported by its own expert declaration describing prior art searches that a skilled searcher would have conducted.

A party is estopped under § 315(e)(1) from requesting a reexamination proceeding based on grounds that the party “raised or reasonably could have raised” during an IPR. The legislative history of § 315(e) defines “reasonably could have raised” as “prior art which a skilled searcher conducting a diligent search reasonably could have been expected to discover.” The PTO cited legislative history stating that “reasonably could have raised” does not require a “scorched-earth search,” leaving open the possibility that a diligent search may not discover a particular reference. But the PTO also distinguished the search an examiner or lawyer may conduct from the more robust search that a skilled searcher is assumed to conduct prior to filing a petition for a IPR proceeding.

The PTO evaluated each of the four references in GITS’s reexamination grounds based on the criteria described above. Two of the references were patent documents available in commercial databases that a skilled searcher could be expected to find. The third reference was a “seminal textbook” that GITS itself stated was used in the field to train those of skill in the art. The textbook reference was also found through standard citation searching of the patent at issue. The fourth reference was provided by a publisher that GITS stated “was an established publisher that was well known to those interested in the field,” and which maintained an online searchable database of its publications. The PTO determined that the fourth reference would have been found by a reasonably diligent search, despite the fact that a subscription fee was required to search the database.

The PTO also weighed the parties’ competing expert searcher declarations and determined that Lisk’s declaration was persuasive. The GITS declaration failed to describe the actual searches that a skilled searcher used to uncover the references relied on in the reexamination, but instead described a less robust search that a attorney conducted. In contrast, Lisk’s declaration described a search conducted by a skilled searcher before filing a petition for an IPR proceeding.

The PTO concluded that estoppel applied because it was more likely than not that the references used by GITS could have been raised during the IPRs. GITS’s certification that estoppel did not apply was found to be improper, and the reexamination was terminated.