Lighting Ballast v. Philips: How the Federal Circuit Reviews Claim Construction

Claim construction decides most patent cases, so the standard an appellate court uses to review it matters a great deal. Lighting Ballast Control LLC v. Philips Electronics North America Corp. was the Federal Circuit’s last full defense of reviewing every aspect of claim construction afresh. Within a year, the Supreme Court had changed the rule, and the change now shapes appeals from both district courts and the Patent Trial and Appeal Board.

The en banc decision (2014)

Since Cybor Corp. v. FAS Technologies, Inc. (Fed. Cir. 1998) (en banc), the Federal Circuit had treated claim construction as a purely legal question reviewed de novo, giving no deference to the trial court. That approach drew criticism: district judges sometimes heard expert testimony and made credibility findings, yet the appellate court could disregard them entirely.

In Lighting Ballast (Fed. Cir. 2014) (en banc), the full court considered whether to overrule Cybor. A majority declined. It reaffirmed de novo review, emphasizing the value of uniform, predictable claim meanings and the principle of stare decisis. Several judges dissented, arguing that factual determinations underlying a construction deserved deference.

Teva v. Sandoz and the remand

The Supreme Court resolved the question in Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc. (2015). It held that Federal Rule of Civil Procedure 52(a)(6) applies to claim construction:

• The ultimate construction is a question of law and is reviewed de novo.
• Subsidiary findings of fact that a district court makes when it consults extrinsic evidence, such as expert testimony about what a term meant to skilled artisans at the time, are reviewed for clear error.
• Constructions based only on intrinsic evidence (the claims, specification and prosecution history) remain legal determinations reviewed de novo.

The Court then vacated the en banc judgment in Lighting Ballast and remanded it for reconsideration in light of Teva. On remand, the Federal Circuit applied Teva’s framework to the district court’s construction.

How the Federal Circuit reviews PTAB claim construction today

Appeals from final written decisions in inter partes review go to the Federal Circuit under 35 U.S.C. § 319. The court reviews Board decisions under the Administrative Procedure Act, but the legal-factual split from Teva carries over:

• The Board’s ultimate claim construction is reviewed de novo.
• The Board’s underlying findings based on extrinsic evidence are reviewed for substantial evidence, the standard that applies to the agency’s fact findings generally.
• Where the Board relied only on intrinsic evidence, its construction gets no deference.

This has practical consequences in PTAB trials. Expert declarations about how a skilled person understood a term can create fact findings that are harder to overturn on appeal than a purely textual reading. The Board’s rules on expert testimony, including the requirement in 37 C.F.R. § 42.65(a) that testimony disclose underlying facts or data, matter for this reason; see evidentiary considerations in PTAB trials.

The standard the Board itself applies has also changed. For petitions filed on or after November 13, 2018, the Board construes claims under the same standard used in civil actions, rather than the broadest reasonable interpretation. See claim construction during inter partes review. That change, together with Teva, means the Board and district courts now apply the same construction standard and are reviewed under parallel legal-factual divisions.

Key takeaways

• Lighting Ballast (Fed. Cir. 2014) (en banc) reaffirmed Cybor’s de novo review of claim construction.
• Teva v. Sandoz (2015) held that subsidiary fact findings on extrinsic evidence are reviewed for clear error; the Supreme Court vacated and remanded Lighting Ballast.
• On remand, the Federal Circuit applied Teva.
• For PTAB appeals, the ultimate construction is reviewed de novo and extrinsic-evidence findings for substantial evidence.