During a Markman hearing, a judge in the Eastern District of North Carolina denied a plaintiff’s request that the defendant be judicially estopped from arguing claim constructions that were different from positions the defendant took in inter partes review (IPR) proceedings before the Patent Trial and Appeal Board (PTAB).

In its petition for IPR, the defendant argued that all claim terms did not require construction and should be accorded their plain and ordinary meaning. The PTAB agreed that no construction was necessary, but ultimately denied institution of IPR.

Thereafter, in the patent infringement case before the district court, the defendant advanced constructions of two disputed claim terms. The plaintiff argued that the defendant had tried to gain an unfair advantage by arguing a broader construction to get the asserted patent invalidated, and a narrower construction to avoid infringement. Meanwhile, the defendant argued that its proposed constructions were simply the plain and ordinary meaning and therefore consistent with its position before the PTAB.

The district court’s memorandum opinion does not consider these arguments. Instead, to decide whether to grant the discretionary relief of judicial estoppel, the court considered three non-exhaustive factors under the relevant regional circuit law:

• The party to be estopped must be asserting a position that is factually incompatible with a position taken in a prior judicial or administrative proceeding.
• The prior inconsistent position must have been accepted by the tribunal.
• The party to be estopped must have taken inconsistent positions intentionally for the purpose of gaining an unfair advantage.

King v. Herbert J. Thomas Mem’l Hosp., 159 F.3d 192, 196 (4th Cir. 1998). Noting that the 4th Circuit considers the third element to be determinative, the district court denied the plaintiff’s request to judicially estop the defendant from arguing two claim constructions. The court stated that “plaintiff failed to show that defendant engaged in malfeasance, purposefully [committed] inequitable conduct, or otherwise intentionally misled this court or the [PTAB],” and that the facts therefore did not compel the “harsh result” of judicial estoppel.

Practice Tip: Accused infringers may be permitted to propose different claim constructions in a proceeding before the PTAB and in an infringement case in district court. The district court’s decision to estop inconsistent claim constructions, however, is discretionary and fact-dependent. Notably, the judge in Panduit did not decide whether the defendant’s claim construction positions were inconsistent, and instead denied judicial estoppel because the plaintiff failed to show that the defendant intentionally misled the PTAB or the district court.

Panduit Corp. v. Corning Incorporated, No. 5:18-CV-229-FL (E.D.N.C. July 2, 2021).