On February 21, 2014, an en banc Federal Circuit decision held (6-4) that the construction of patent claims by a district court is subject to de novo review on appeal, thereby reaffirming Cybor Corp. v. FAS Technologies, Inc., 138 F.3d 1448 (Fed. Cir. 1998)(en banc).


Lighting Ballast Control LLC brought an action for infringement of a patent directed to an electronic ballast (for fluorescent lighting). The claims at issue required “voltage source means” providing constant or variable DC voltage, and the issue was whether the voltage source means was a means-plus-function limitation under 35 U.S.C. § 112 ¶ 6. The district court held that it was not, and the jury returned a verdict of infringement.

On January 2, 2013, a panel decision of the Federal Circuit (Rader, O’Malley and Reyna) reversed the district court. Lighting Ballast Control LLC v. Philips Electronics North America Corp., 498 Fed. Appx. 986 (Fed. Cir. 2013)(unpublished opinion). The panel deemed the question of whether the “voltage source means” fell within the scope of 35 U.S.C. § 112 ¶ 6 to be one of law, reviewed without deference pursuant to Cybor. The panel then held the claims at issue invalid, given that the specification contained no corresponding structure for the claim term, as § 112 ¶ 6 mandates. The panel concluded that plaintiff’s expert testimony that the claim limitation itself implied structure, was insufficient to rebut the presumption that means-plus-function claiming applied.

By Order dated March 15, 2013 the Federal Circuit vacated the panel decision and requested the parties to file new briefs, addressing inter alia whether Cybor should be overruled, and whether the Federal Circuit should accord any deference to a district court’s claim construction. 

The Order also invited the U.S. Patent and Trademark Office to submit an amicus brief, and the Office did so. In that brief, the Office argued that while the proper scope of a patent claim is ultimately a question of law, and that Cybor should be affirmed in that respect, certain subsidiary findings of fact (such as the historical meaning of a claim term) were entitled to deference on appeal, under Rule 52(a) of the Federal Rules of Civil Procedure, and that Cybor should be overruled to that extent.

The En Banc Decision

In an Opinion by Judge Newman, joined by Judges Dyk, Prost, Moore, Taranto and Lourie (who also wrote a concurring opinion), the majority affirmed the Cybor standard of de novo review of claim construction, considering it an implementation of the Supreme Court’s decision in Markman v. Westview Instruments, Inc., 517 U.S. 370 (1996). The majority stressed the principle of stare decisis, noting that Cybor was fifteen year old case law which had been applied in many hundreds of decisions, yet Congress had not decided to alter that decision, and there had been no demonstration that Cybor had proven unworkable.

The majority also rejected the introduction of a fact/law distinction (as the USPTO argued), stating that it could increase burden by adding a new and uncertain inquiry, namely the disentangling of fact from the application of law to fact. The majority also noted that deferential review could result in different court rulings on close questions of claim construction both being affirmed – with the result that claims could be accorded different meanings in different courts, and restore the forum shopping the Federal Circuit was created to avoid. The majority did not see Civil Procedure Rule 52(a) as dispositive, since while it prescribed the standard of review for questions of fact, the rule itself did not determine what was to be properly characterized as a question of fact within its scope. Thus, in view of the majority decision not to overrule or modify the Cybor standard, the panel decision was reinstated.

The dissenting opinion by Judge O’Malley, who was joined by Judges Rader, Reyna and Wallach, asserted that the majority opinion was inconsistent with Rule 52(a) (6), requiring trial court findings of fact not to be set aside unless clearly erroneous. The dissent further argued that the Cybor court itself misapprehended the Supreme Court’s Markman decision, and that its allocation of claim construction to the court, rather than the jury, did not make the trial court’s subsidiary factual determinations underlying claim construction outside the deference Congress mandated such determinations under the Federal Rules of Civil Procedure.

Sean M. McCarthy