Sounding Off: Prosecution Disclaimer Requires Unambiguous Intrinsic Evidence


Before Newman, Reyna, and Stoll. Appeal from the Western District of Washington.

Summary: A finding of prosecution disclaimer must be supported by an unambiguous disavowal within the intrinsic record.

Genuine sued Nintendo, alleging infringement of U.S. Patent No. 6,219,730 (’730 patent). ’730 patent claim 1 is generally directed to an apparatus coupled to a computer that uses an “input signal.” During prosecution the patentee distinguished prior art on the basis that the art did not disclose “signals containing audio or higher frequencies.” The parties agreed that these arguments resulted in a prosecution disclaimer, but disagreed as to the scope of the disclaimer. Genuine argued the disclaimer only applied to signals lower than a minimum audio frequency of about 20 Hz. Nintendo, however, submitted an expert declaration interpreting the prior art and argued the disclaimer should extend to signals up to 500 Hz. The court agreed with Nintendo and construed the term “input signal” as limited to signals with a frequency above 500 Hz, and granted Nintendo’s motion for summary judgment of non-infringement.

Genuine appealed the grant of summary judgment, and the Federal Circuit reversed. The Federal Circuit explained that the district court erred by using the extrinsic expert declaration to contradict the prosecution history’s intrinsic evidence when constructing the claim. The Federal Circuit found that the only unambiguous disclaimer in the intrinsic record was to signals below 20 Hz, stemming from the consistent distinction of the prior art’s “slow-varying signals” from the patent’s “audio or higher frequency” input signals. In contrast, the intrinsic record did not support the district court’s finding of disclaimer of input signals of up to 500 Hz. Because prosecution disclaimer does not apply to statement that are “ambiguous or amenable to multiple reasonable interpretations,” and the only unambiguous statement disclaimed signals below the audio spectrum, the Federal Circuit held the district court erred in its construction of “input signal.” In view of this incorrect claim construction, the Federal Circuit reversed the grant of summary judgment and remanded for further proceedings.

Editor: Paul Stewart