Claim construction decisions made by district judges during patent litigation will continue to receive plenary review on appeal, according to a recent en banc decision by the United States Court of Appeals for the Federal Circuit. In Lighting Ballast Control LLC v. Philips Electronics North America Corp., No. 2012-1014 (Fed. Cir. Feb. 21, 2014), the court voted 6–4 to retain the existing de novo, or non-deferential, standard of review.

Claim construction describes the process courts use to interpret claim language in a patent. Because the claims define the scope of patent protection, fundamental issues of patent infringement or validity can often hinge on the true meaning of even a single disputed word in a claim. In 1996, the Supreme Court held that judges, not juries, should resolve claim construction disputes. Markman v. Westview Instruments, Inc., 517 U.S. 370 (1996). But the Court did not clearly spell out whether an appeals court should defer to trial court claim construction decisions—that is, does a trial judge’s perspective offer special advantages for divining the correct claim interpretation, or can a panel of appellate judges do as well reviewing the patent documents and the trial record?

Soon after Markman, the Federal Circuit answered that claim construction is a fundamentally legal issue best suited to non-deferential review. Cybor Corp. v. FAS Techs., Inc. 138 F.3d 1448 (Fed. Cir. 1998) (en banc). In the ensuing fifteen years, that decision engendered much commentary and debate, culminating in the Federal Circuit’s decision to revisit the question in Lighting Ballast.

In Lighting Ballast, the six-judge majority reaffirmed the de novo standard of review for claim construction decisions. The majority rested its decision primarily on a conclusion that experience after Cybor has not revealed any compelling reason to modify straightforward, effective, and now well-established claim construction practices by introducing a new standard likely to upset settled expectations in the patent system. The court also cited falling reversal rates in the years since Cybor was decided. Judge Lourie wrote a concurring opinion emphasizing that, despite the ostensible de novo standard, the Federal Circuit respects district judges’ claim construction decisions and routinely applies a measure of informal deference on appeal. The four dissenters argued that claim construction necessarily includes disputes of fact that trial judges are uniquely positioned to decide, that the majority’s decision runs contrary to prevailing legal standards, and that de novo review inhibits settlement and prolongs litigation.

For now, Lighting Ballast means that federal courts’ claim construction decisions will continue to receive de novoreview. The decision is a possible candidate for Supreme Court review, however, especially given its central importance for patent litigation and the Supreme Court’s frequent intervention on patent law issues in recent years.  

The court’s decision and a recording of the en banc oral argument are available from the Federal Circuit’s website.