District Court Finds Patentee’s Prior Statement Regarding Prior Art A Binding Admission

In The Sherwin-Williams Company v. PPG Industries, Inc., 2-17-cv-01023 (WDPA 2021-01-21, Order), the court had to decide whether Plaintiff The Sherwin-Williams Co. (“Sherwin”) should be bound by its prior admission to the United States Patent and Trademark Office (“USPTO”) during vacated reexamination proceedings.  

During one of the reexamination proceedings, Sherwin admitted that certain prior art (“Perez”) disclosed a BPA-free coating, although it contended that its patents were valid for other reasons.  Subsequently, the entire reexamination proceeding was terminated without any action on the merits.  

Thereafter, in its invalidity contentions in the current litigation, Sherwin contended that Perez did not disclose a BPA-free coating and the admissions during reexamination did not admit that Perez disclosed or rendered obvious a certain limitation. In its initial expert report, Defendant PPG Industries’ (“PPG”) technical expert noted Sherwin’s admission to the USPTO that Perez disclosed a BPA-free coating.  In response, Sherwin’s expert opined that Perez did not disclose a BPA-free coating.  

PPG then contended that Sherwin is bound by its admission to the USPTO that Perez discloses a BPA-free coating and that its expert’s opinions to the contrary must be excluded from evidence. Sherwin argued that it should not be bound by the statement its attorney made during the reexamination proceeding. 

The court, however, found Sherwin’s statement in the reexamination proceeding was not an off-the-cuff comment by an attorney during oral argument. Instead, it was an unambiguous position taken by a party in a written brief filed three months after the USPTO decision.  The court further reasoned PPG is entitled to rely on the position Sherwin took at the USPTO.  Thus, the Court found Sherwin is bound by the position it took at the USPTO that Perez discloses a BPA-free coating.  

The court reasoned that the “prosecution history, which includes ‘all express representations made by or on behalf of the applicant to the examiner to induce a patent grant,’ limits the interpretation of the claims ‘so as to exclude any interpretation that may have been disclaimed or disavowed during prosecution in order to obtain claim allowance.’”  Thus, “a patentee’s representations to the PTO during the prosecution of its patent application about the scope of the prior art is a binding admission and should ‘be accepted at face value’ during subsequent litigation over the patent.”  This principle that a party’s admissions during prosecution are binding “applies with equal force to arguments made by a patentee to sustain the patentability of claims during reexamination.”  And, when the prosecution history is clear, and the public entitled to rely on it, proffered inconsistent expert testimony is not probative and is not admissible to contradict the record.

In this case, the court found Sherwin made a clear statement to the examiner in its efforts to distinguish the prior art references during prosecution. That statement is part of the record and can be relied upon by the public. Sherwin cannot take the position that Perez is BPA-free to obtain the patent and assert a contrary position in the lawsuit. Thus, the court held the proffered inconsistent expert testimony by its expert is not probative and is not admissible.  

This case serves as a strong reminder to always be careful what you argue to the USPTO during prosecution or reexamination of a patent.  Clear explicit statements used to distinguish the prior art references can create representations to the USPTO about the scope of the prior art. Those representations can then create binding admissions that can be used in subsequent attempts to enforce the patent.  Similarly, when enforcing a patent, it is always important to check the prosecution history to ensure nothing contained therein could be used as an admission to limit the scope of the patent or the arguments that can be made about it.