In a split en banc decision, the Federal Circuit maintains de novo review of claim construction.

The Federal Circuit granted the en banc petition filed by patentee Lightning Ballast Control to reconsider the Cybor standard requiring that claim construction decisions be reviewed de novo on appeal. The appellate panel had reviewed the district court’s construction of the term “voltage source means” de novo, reversed the district court, and held the claims containing that term invalid for indefiniteness.

The majority opinion, authored by J. Newman, and joined by J. Lourie, Dyk, Prost, Moore, and Taranto, confirmed the Cybor standard, following principles of stare decisis. In so doing, the court rejected the arguments put forth by the patentee and various parties amici. First, the court rejected the view that patent claim construction is most reasonably classified as a question of fact, and is entitled to a clear error standard. Second, the court rejected the view that the factual elements of claim construction should be reviewed under a clear error standard, while the final conclusion should be reviewed de novo as a matter of law. In rejecting these arguments, the court examined post-Cybor developments over a period of 15 years which may have undermined the reasoning of Cybor as well as demonstrations that Cybor has proved unworkable, but found none. The majority commented that the proponents of overruling Cyboridentified no pattern of error and presented no indictment of inferior results. As those proponents did not meet the demanding standards of the doctrine of stare decisis, the court found that there was neither a “grave necessity” nor “special justification” for departing from Cybor.

The dissenting opinion, authored by J. O’Malley, and joined by J. Reyna and Wallach, stated that the proper standard of review for claim construction is one where the Federal Circuit defers to the findings of fact intrinsic in a claim construction decision unless they are clearly erroneous. The dissent provided examples of such factual issues, such as the meaning of claim terms by those of skill in the art at the time, the relevance and weight to be given to text or treatises, the determination of the level of skill in the art, and others.

A copy of the opinion can be found here.