Federal Circuit Reinforces Strict Application of Prosecution History Disclaimer

The United States Court of Appeals for the Federal Circuit has recently reinforced the consequences of prosecution history disclaimer. In Puradigm, LLC v. DBG Group Investments LLC, the court held that statements made during prosecution can permanently narrow claim scope, even when the examiner rejects those arguments and the applicant moves on. This decision serves as a reminder that statements made during prosecution can have lasting consequences, even if those statements are ignored.

Key Takeaways:

• Statements made to distinguish prior art can have lasting consequences, even if the examiner rejects those arguments.
• Applicants should exercise judgment when characterizing prior art in office action responses.
• Where appropriate, applicants should expressly clarify or withdraw statements that could later be read as limiting.

The patent at issue, U.S. Patent No. 8,585,979, relates to photo-catalytic air purification systems that use ultraviolet (UV) light to activate a catalyst-coated target to generate ions for removing airborne contaminants. Further, the claimed system of the ‘979 patent uses a “specular UV reflector” that reflects a single incoming light ray in a single outgoing direction, in contrast to conventional systems that rely on “diffuse” reflection where an incoming ray is reflected into a broad range of directions.

During prosecution, the examiner cited U.S. Patent No. 6,500,387 (“Bigelow”), as disclosing the claimed “specular UV reflector.” In response, the applicant argued that Bigelow did not disclose a specular UV reflector, either expressly or inherently. The examiner disagreed and maintained the rejection, taking the position that Bigelow’s polished aluminum reflector produced mirror-like reflection, which satisfied the “specular UV reflector” limitation. The applicant did not withdraw or further comment on its position but instead proceeded with amendments adding other features while retaining the “specular UV reflector” limitation. Following these amendments, the examiner ultimately allowed the claims based on the inclusion of both first and second specular UV reflectors configured to direct UV energy to the photo-catalytic targets.

In the case at hand, Puradigm, the assignee of the ‘979 patent, sued DBG for infringement based on products using unpolished aluminum reflectors. The district court granted summary judgment of noninfringement, concluding that the applicant disclaimed polished aluminum reflectors from the scope of the claims during prosecution and that this reasoning also applied to unpolished aluminum. The Federal Circuit affirmed.

On appeal, the Federal Circuit considered two arguments from Puradigm, who argued that there was no prosecution history disclaimer and that the district court did not properly construe “specular UV reflector.” The court rejected both arguments and held that the applicant made a clear and unmistakable disclaimer during prosecution that was never qualified or withdrawn. As a result, the term “specular UV reflector” could not be interpreted to include the accused unpolished aluminum reflectors.

In arriving at its decision, the court explained that disclaimer can apply even if the examiner rejects the underlying argument, because the focus remains on the applicant’s statements. Consistent with this principle, the court further emphasized that the public has a right to rely on those statements without needing to determine whether the examiner relied on them. The court then turned to whether any such disclaimer had been negated, explaining that it may consider whether the applicant retracted prior statements distinguishing the prior art or acquiesced to the examiner’s position. However, the court found that the applicant did neither. The applicant did not withdraw its earlier statements and did not adopt the examiner’s position, therefore leaving the disclaimer intact.

In light of the disclaimer, the court agreed with the district court that the disclaimer excluded polished aluminum reflectors and framed the remaining issue as whether that exclusion also covered unpolished aluminum. The court concluded that it did, explaining that unpolished surfaces produce more diffuse reflection and less specular reflection than the polished surfaces in Bigelow. As a result, the accused products fell outside the scope of the claims and summary judgment of noninfringement was proper.