In a rare reversal of the patent-savvy Judge Ward of the U.S. District Court for the Eastern District of Texas, the U.S. Court of Appeals for the Federal Circuit vacated a jury verdict of infringement and vacated a permanent injunction finding that it was legal error for the district court not to construe a disputed but "well understood" claim term and to instruct the jury on the doctrine of equivalents in a case in which the only claim term for which the doctrine of equivalents was argued was added by amendment for purposes of patentability. O2 Micro Int'l Ltd.v. Beyond Innovation Tech. Co., et al, Case No. 07-1302 (Fed. Cir., April 3, 2008) (Prost, J.).
O2 Micro brought an infringement action alleging that BiTEK's inverter controllers infringed several claims of O2 Micros patents pertaining to switches for controlling the amount of power (load) on DC to AC converter circuits. During prosecution, the examiner rejected the claims of one of the asserted patents as obvious over the prior art. In response, O2 Micro added a limitation to each of the independent claims reciting that drive circuitry caused the switches to power their loads "only if" a feedback signal was above a predetermined threshold. Following the amendment, the examiner allowed the claims.
Except for two circumstances in which the accused switches continued to power their loads even after the feedback signal was below the predetermined threshold, defendants conceded that BiTEK's controllers generally practiced the asserted patents. Thus, defendants non-infringement position hinged on the accused products not satisfying the "only if" limitation.
During Markman proceedings, defendants argued that the claim term "only if" should be construed by the court and proposed a construction consistent with its non-infringement position. O2 Micro argued that no construction was necessary because the phrase "only if" consisted of "two simple plain English words." The district court recognized that the parties disputed whether the term allowed for an exception, but declined to construe the term "only if" because it had a "well-understood definition." During trial, all parties, including O2 Micro, submitted evidence relating to the meaning of the claim term "only if." O2 Micro additionally argued for infringement of the "only if" limitation under the doctrine of equivalents. At the conclusion of trial, the district court read jury instructions that included an explanation that a claim limitation may be satisfied under the doctrine of equivalents. The jury found infringement of all the asserted claims of the patents at issue. The defendants appealed, arguing it was legal error not to construe "only if" and to instruct the jury on the doctrine of equivalents.
The Federal Circuit agreed that it was legal error for the district court not to construe "only if": "[w]hen the parties raise an actual dispute regarding the proper scope of [] claims, the court, not the jury, must resolve that dispute." The Court further explained, "[a] determination that a claim term 'need no construction' or has the 'plain and ordinary meaning' may be inadequate when a term has more than one 'ordinary' meaning or when reliance on a term's 'ordinary' meaning does not resolve the parties' dispute&[T]he district court failed to resolve the parties dispute because the parties disputed not the meaning of the words themselves, but the scope that should be encompassed by this claim language." While recognizing that it was not the district court's duty to construe every limitation present in a patent's asserted claims, the Federal Circuit held that when the parties present a fundamental dispute as to the scope of a claim term, the district court should resolve it.
Further, the Federal Circuit found that it was legal error for the district court to instruct the jury on infringement under the doctrine of equivalents. The Court found that the amendment adding "only if" to the claims was made for purposes of patentability and that the presumption of surrender under Festo had not been rebutted. The Court reasoned that "only if" was not merely tangential to the amended limitation because the objectively apparent reason for the amendment was to require the feedback circuit to be operational "only if said feedback signal is above a predetermined threshold." Thus, the Court concluded that the doctrine of equivalents instruction was in error because prosecution history estoppel prevented equivalents for that particular claim limitation.
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