For Indefiniteness Challenges in District Court, Don’t Forget What You Said in IPR

A recent district court decision illustrates that petitioners should think carefully about requesting IPRs of claims that they may challenge as indefinite in litigation. Indefiniteness challenges are not permitted during an IPR. However, a PTAB decision during IPR may influence a district court’s ruling on an indefiniteness challenge raised in the litigation.

In American Technical Ceramics Corp. v. Presidio Components, Inc., No. 2:14-cv-06544, D.I. 126 (E.D.N.Y., March 27, 2018), a patent-in-suit recited “substantially L-shaped terminations” that extend “negligibly over a top surface” of a device body. The defendant argued in district court that claims in this patent were indefinite because there was no reasonably certain standard for determining what constitutes a “substantially L-shaped termination” or a “negligible” amount of termination. Under the Supreme Court’s decision in Nautilus, Inc. v. Biosig Instruments, Inc., 134 S. Ct. 2120 (2014), claims are indefinite if they “fail to inform, with reasonable certainty, those skilled in the art about the scope of the invention.”

The district court denied the defendant’s motion for summary judgment that the claims of the patent with these terms were indefinite. The district court’s decision was due in part to an earlier decision in an IPR brought by the defendant in which the PTAB construed the claim term that the defendant was alleging to be indefinite in the litigation. The court noted that for the PTAB to have issued a decision that “necessarily involved construction and application of the terms,” it must have been possible for the PTAB to understand the scope of the patent.


Although IPRs are often an expedient way for a party accused of infringement to challenge the asserted patent, they have always involved certain tradeoffs. This case illustrates one potential tradeoff: asserting that prior art discloses a limitation in IPR may be viewed as evidence that the limitation can be interpreted and is not indefinite. The decision to petition for IPR should not be made without careful consideration of such tradeoffs.

This case also has implications for the timing of indefiniteness challenges in district court. Parties should be aware that they might have difficulty obtaining judgment of indefiniteness of a claim that has already been construed, either by a district court or by the PTAB. Thus, defendants should consider a motion to dismiss on the basis of indefiniteness, which might work for some claims, and may be complete before the deadline to petition for IPR.


This post was co-authored by a summer associate in the Litigation Group, Michelle Bone.