Is "Burying" Important Prior Art In A Large Number Of Insignificant References Inequitable Conduct In USPTO Patent Prosecution?

• Published date: 05 September 2023
• Subject Matter: Intellectual Property, Patent
• Law Firm: Osha Bergman Watanabe & Burton LLP
• Author: Sarah Bittner, Ph.D.

Several recent cases illustrate a continuing and evolving split among the different federal district courts as to whether a defense of inequitable conduct can successfully be based on "burying."

The U.S. Court of Appeals for the Federal Circuit (CAFC) in Therasense¹ set the current standard for inequitable conduct. While the CAFC recognized burying examiners with a deluge of prior art references -- most of which have marginal value -- as a problem straining the USPTO's resources and contributing to a backlog of administrative work, the Court did not decide in that particular case whether a defense of inequitable conduct can be successfully based on burying. Burying here means submitting one or more highly material prior art references along with a large group of relatively insignificant references in an information disclosure statement (IDS), or series of IDSs. To constitute inequitable conduct under Therasense, it would seem that the burying must be done with deceptive intent and the "buried" reference must be but-for material. Several recent cases illustrate a continuing and evolving split among the different federal district courts as to whether a defense of inequitable conduct can successfully be based on "burying."

In a July 2023 decision by the U.S. District Court for the Northern District of Illinois,²Illinois Tool Works, Inc. (ITW) had sued its competitor Termax, LLC for infringing two patents relating to automotive component fasteners. Termax filed a petition in the Patent Trial and Appeal Board (PTAB) for Inter Partes Review (IPR) of one of the two patents, and successfully invalidated the patent during the pendency of the district court case. In the meantime, ITW prosecuted an application for a third patent in the USPTO. In an IDS submitted during prosecution of that third patent, ITW submitted the PTAB's final decision invalidating one of the two original patents-in-suit. When the third patent was granted, ITW amended its complaint against Termax to allege infringement of the new (i.e., third) patent instead of the PTAB-invalidated one. In the IDS in question, ITW submitted seven non-patent references including the PTAB's final decision.

With regard to ITW's third patent, Termax alleged that ITW committed inequitable conduct by burying the PTAB's decision invalidating the previously-asserted patent in a multiplicity of other references in the IDS, and by failing to draw the examiner's attention to a particularly relevant part of the PTAB's...