On December 5, 2023, Director Jason A. Fitzsimmons and Counsel Richard A. Crudo presented “Developments in IPR Estoppel.” The program focused on recent decisions from the Federal Circuit, Patent Trial and Appeal Board (PTAB), and district courts that have shaped the contours of inter partes review (IPR) estoppel under 35 U.S.C. § 315(e), which bars a petitioner from asserting invalidity grounds in district court that were “raised or reasonably could have [been] raised during” the IPR.

The presenters discussed how companies and practitioners can invoke (or avoid) both statutory estoppel involving newly discovered art and product art, as well as common law estoppel across proceedings.

Below are some key takeaways and related resources:

  1. Parties should adduce evidence of what a skilled searcher would do. The Federal Circuit’s recent Ironburg decision holds that § 315(e) bars a petitioner from asserting invalidity grounds that “a skilled searcher conducting a diligent search reasonably could have been expected to discover.” The patent owner bears the burden of showing that the reference would have been found. To satisfy that burden, patent owners should consider performing their own prior art searches using key terms found in the challenged patents, but should balance the advantages of such searching with the risk of uncovering prior art that may be discoverable in litigation. Patent challengers, by contrast, should record their search methodologies and poke holes in patent owners’ evidence, including by showing that patent owners’ searches are infected by hindsight bias. For more information, see Ironburg and the Elusive “Skilled Searcher” Estoppel Standard for Newly Discovered Prior Art (R. Crudo, Sept. 2023).
  2. Parties should be aware of various district court approaches to estoppel as applied to product art. As a general matter, § 315(e) estoppel does not apply to product art because such art cannot be raised in an IPR. But courts have taken different approaches for determining whether estoppel applies to a product that is similar to a printed publication that is raised in an IPR. One line of cases takes a narrow view of estoppel and holds that the product constitutes a different ground such that estoppel would not apply. Another line of cases takes a broad view and holds that if the product merely constitutes different evidence of the same ground then estoppel would apply. Still another line of cases takes a middle-ground view and imposes a burden-shifting framework that focuses on whether the product’s material limitations are also disclosed in the printed publication. Practitioners should know the law in their jurisdiction and, if no law is established, advocate for the most favorable law. And, to avoid estoppel, challengers should consider relying on non-public evidence describing product art (that could not have been raised in an IPR) rather than printed publications.
  3. Parties should be cognizant of whether and to what extent common law estoppel can apply when statutory estoppel does not apply. While collateral estoppel is unlikely to apply from a PTAB proceeding to bar a patent challenger from asserting invalidity in district court, it can apply in some circumstances against patent owners, as well as to discrete issues that were actually adjudicated by the PTAB. Further, unlike statutory estoppel, collateral estoppel applies not just to claims that were subject to a final written decision, but also as to substantially similar claims. Accordingly, to avoid the effects of estoppel, patent owners should preserve meaningful differences between patent claims in a family so that one patent’s invalidity will not infect others. By contrast, challengers should point to similarities between previously invalidated claims and the claims at issue. And both patent owners and challengers should consider whether collateral estoppel can apply to prevent the PTAB (or the other party) from taking inconsistent positions across IPRs. For more information, see IPR Estoppels: A Power Imbalance for Plaintiffs and Defendants (J. Tuminaro, P. Cloud, Mar. 2022); Beware of Collateral Estoppel at the PTAB (J. Fitzsimmons, I. Attenborough, May 2023).

To learn more about specific case law impacting estoppel, and practical tips for patent owners and patent challengers, watch our webinar recording or contact us.


Note: CLE is not available for On Demand viewing.

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