On March 15, 2013, the United States Court of Appeals for the Federal Circuit ordered a rehearing en banc in Lighting Ballast Control, LLC v. Philips Elecs. N. Am. Corp, et al.1 This order sets the stage for a potential change in the appellate standard of review of district courts' claim construction decisions.

By its order, the court vacated its January 2, 2013 opinion, in which it had reversed a panel finding that Lighting Ballast's patent claims were not invalid for indefiniteness. In so doing, the Federal Circuit explicitly directed the parties to brief whether the court should overturn its 1998 decision in Cybor Corp.,2 and whether deference should be afforded to any aspect of a district court's underlying claim construction findings. In essence, the issue before the en banc court will be whether it should abandon the de novo standard of review for claim construction.

Since Cybor Corp., there has been growing sentiment that the increasing volume, unpredictability, and costs of patent litigation are at least partly attributable to the de novo standard, with critics citing the opportunity for patentees to continue to prosecute their cases in spite of adverse decisions at the district court level.

The District Court Proceedings

On August 19, 2010, the United States District Court for the Northern District of Texas issued a declaratory judgment that the asserted claims of Lighting Ballast's U.S. Patent No. 5,436,529, which covered control and protection circuits for lighting ballasts used in fluorescent lamps, were invalid for indefiniteness.3 The central issue below was whether Lighting Ballast had expressed a "means-plus-function" limitation that triggered Section 112, Paragraph 6 of the Patent Act.4 Under Section 112, Paragraph 6, a patentee is permitted to claim an invention in terms of its function, so long as an underlying "structure"—the "means for" performing that function—is adequately disclosed in the patent specification.

The law is not precise as to when Section 112, Paragraph 6 applies, although, courts generally consider the statute triggered when the word "means" appears in a claim. ULT, the alleged infringer, argued that Section 112, Paragraph 6 applied for this reason. Accordingly, ULT argued that the asserted claims were invalid for Lighting Ballast's failure to disclose a structure in its specification supporting the claimed "means-plus-function" limitation.5 The district court agreed, holding Lighting Ballast's claims invalid for indefiniteness.

On December 2, 2010, the district court revised its original finding of indefiniteness following an expanded factual inquiry, including expert testimony and a jury verdict.6 Subsequently, the district court reversed itself, finding that the context of Lighting Ballast's claim language, alone, expressed sufficient structure to avoid implicating Section 112, Paragraph 6 altogether, negating its prior ruling that the claims were indefinite. ULT then appealed the findings of validity and infringement to the Federal Circuit.

Appeal to the Federal Circuit

On January 2, 2013, the Federal Circuit reviewed the district court's claim construction findings, de novo, per the standard announced in Cybor Corp., and reversed the district court, substituting its own findings of fact underlying claim construction.7 Using much the same reasoning as the original district court decision, the Federal Circuit found that the claims expressed a "means-plus-function" limitation that indeed implicated Section 112, Paragraph 6, and, as such, further found that no corresponding structure was sufficiently disclosed in the patent specification. Lighting Ballast then moved for rehearing, en banc, resulting in the March 15, 2013 order.