In its first ruling on the scope of estoppel under 35 U.S.C. §315(e)(1) following a final IPR decision, the Board has denied institution of trial in a second IPR involving the same patent. The case, Dell, Inc. v. Electronics & Telecommunications Research Institute, IPR2015-00549 (PTAB March 26, 2015) (paper 10), involved an IPR brought in connection with U.S. patent no. 6,978,346. As a result of a final decision issued in a previously-instituted IPR involving the same patent, the PTAB determined that challenges to claims 1-3 and 5-8 of the ’346 patent were precluded under the estoppel provisions governing IPRs. In its ruling, the Board explained that the legislative history of the estoppel provisions suggests a broad interpretation of the scope of estoppel.
In IPR2015-00549 (“the ’549 IPR”), Petitioner challenged claims 1-9 of the ’346 patent on obviousness grounds. The petition was filed on January 8, 2015, and relied on prior art references identified as Mylex and Hathorn. Patent Owner filed a waiver of preliminary response on Feb. 3, 2015.
Petitioner had previously challenged claims 1-9 of the ’346 patent in IPR2014-00635 (“the ’635 IPR”) on a variety of anticipation and obviousness grounds, relying on Mylex, Hathorn and other prior art references. On March 20, 2014, the PTAB instituted trial in the ’635 IPR on the sole ground that claims 1–3 and 5–8 were anticipated under 35 U.S.C. §102(b) by Hathorn. IPR2014-00635, paper 19 (decision on institution) at 23–24. The Board denied all other grounds on the merits. Id. After conducting trial in the ’635 IPR, the PTAB issued its final written decision on February 27, 2015. In its decision, the PTAB determined that Petitioner failed to prove by a preponderance of the evidence that claims 1–3 and 5–8 of the ’346 patent were unpatentable. IPR2014-00635, paper 39 (final decision) at 24.
Ruling on Estoppel
After issuing its final decision in the ’635 IPR, the Board considered whether to institute trial in the ’549 IPR. Even though Patent Owner filed a waiver of its preliminary response in the’549 IPR (and, thus, did not assert estoppel), the Board raised estoppel sua sponte in its institution decision:
Under 35 U.S.C. § 315(e)(1), once a Petitioner has obtained a final written decision, that Petitioner may not request or maintain subsequent proceedings on a ground that it ‘could have raised’ during the prior proceeding.
IPR2015-00549, paper 10 at 4. The PTAB identified two predicate requirements for estoppel to apply – first, the petitioner 1 in the subsequent proceeding must be the same as the petitioner in the prior proceeding; and second, there must be a final written decision in the prior proceeding under 35 U.S.C. § 318. Id. The Board determined that both of these requirements were met. Id.
The Board then turned to the heart of the estoppel issue: what grounds Petitioner “could have raised” in the prior ’635 IPR – in other words, what is the scope of estoppel. As a question of first impression, the PTAB looked to the legislative history of the AIA. Citing a statement by Senator Grassley, the Board explained that what a petitioner “could have raised” should be broadly construed to include:
prior art which a skilled searcher conducting a diligent search would reasonably  have been expected to discover.
Id. (quoting 157 Cong. Rec. S1375 (Mar. 8, 2011)) (emphasis added). According to the Board, such a broad scope of estoppel serves the purpose of preventing a party from bringing serial challenges to a patent. Id. at 4-5.
Ultimately, the Board did not find it necessary to evaluate what a diligent search would have uncovered, because the prior art references asserted in the ’549 IPR were also asserted (albeit on different grounds) in the previous ’635 IPR. For example, one of the two ’549 IPR references, Hathorn, was asserted as the basis of an anticipation ground in the ’635 IPR. Similarly, the second of the two ’549 IPR references, Mylex, was asserted as one of a combination of references in several obviousness grounds in the ’635 IPR. But the differences in how these prior art references were applied in the ’549 IPR and in the previous ’635 IPR was of no import to the Board. Indeed, the Board found immaterial the fact that Petitioner changed its belief as to how the Hathorn reference should be applied during trial in the ’635 IPR. Rather, the fact that both references were known to Petitioner at the time of the ’635 IPR was deemed sufficient to trigger the estoppel. Id. at 5-6.
1 This case did not present the issue of a petitioner’s real party in interest or privy who would also be subject to estoppel.
Implications of the Estoppel Ruling
This ruling may have far-reaching effect on subsequent cases where estoppel may be triggered. First, the PTAB adopted a broad reading of the potential scope of estoppel, to include prior art that a “skilled searcher” could have discovered conducting a “diligent search.” Thus, the mere fact that a prior art reference was unknown to a particular patent challenger would not be enough to avoid application of the estoppel provisions; if the reference could reasonably have been discovered by someone with experience in conducting thorough prior art searches, it is likely that the reference could be used by a patent owner to trigger estoppel.
Second, a party’s interpretation (or reinterpretation) of what a prior art reference teaches, and how it stacks up against claim elements, likely cannot be used to avoid the application of estoppel. As shown by the ruling, the Board will not give any weight to reasons why a party may have applied a reference one way in a first proceeding and another way in a later proceeding. This will likely be the case even if the change in position results from a claim interpretation or ruling on what the prior art teaches by the PTAB or other tribunal. To avoid this estoppel effect, a petitioner would need to include alternative arguments or grounds in a common petition or in contemporaneously-filed petitions.
Finally, the Board’s ruling on the scope of estoppel points to several factors that may become the subject of dispute if estoppel is raised. For example, parties may dispute what is a skilled searcher (e.g., the level of education or experience), what constitutes a diligent search (e.g., what sources should be reviewed, what search parameters to use), and what would the skilled searcher reasonably have been expected to discover (e.g., is the reference likely to have been uncovered given the skill level, sources and search parameters used). These factors may vary based on the technology involved. Disputes over these factors may give rise to additional evidentiary submissions to support each party’s position. Further, parties may attempt to obtain discovery directed to an opponent’s discovery of the reference.