In Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc., the Supreme Court addressed the question of what the standard of review should be for patent claim construction. In its decision on January 20, 2015, the Court held that a federal appellate court could only overturn a district court’s factual findings if those findings were determined to be clearly erroneous. This holding modifies the longstanding de novo standard used by the Federal Circuit when reviewing claim construction. While trying to generate certainty for district court claim construction decisions and decrease the reversal rate of claim construction decision by the Federal Circuit, the Federal Circuit may focus on the legal analysis and intrinsic evidence to keep claim construction de novo.

The case involves a patent dispute over the multiple-sclerosis drug Copaxone. Teva Pharmaceuticals owns several patents directed to copolymer-1, which is the active ingredient found in Copaxone. Teva sued Mylan and Sandoz for infringement based on their applications seeking FDA approval to produce and market generic versions of Copaxone.

At issue before the district court was how to construe the term “molecular weight.” Sandoz argued that the term “molecular weight” in the claims at issue was indefinite because it was unclear how the molecular weight was calculated. In support of this indefiniteness argument, Sandoz proposed three different definitions for “molecular weight.” However, based on the specification, prosecution history, and testimony from Teva’s expert, the District Court construed the term to mean peak average molecular weight and therefore found no ambiguity based on what a person having skill in the art would understand “molecular weight” to mean. Consequently, the district court held that the Sandoz and Mylan products infringed on Teva’s patents. On appeal, the Federal Circuit applied a de novo standard of review and reversed, reasoning that the term “molecular weight” is indefinite because the claims do not indicate which molecular weight measure is intended.

The Supreme Court granted Teva’s petition for writ of certiorari to address whether a district court’s finding of fact in the construction of a patent claim should be reviewed de novo, as the Federal Circuit requires, or for clear error, as Federal Rule of Civil Procedure 52(a) requires. Teva argued that Federal Rule of Civil Procedure 52(a) requires deferential review of fact-findings, even when a question of law rests on these fact-findings. Further, Teva argued that fact-findings regarding the state of the art are entitled to deference. On the other hand, Sandoz argued that since claim construction is a “purely legal” question, Federal Rule of Civil Procedure 52(a) does not apply.

In a 7-2 majority, the Supreme Court reversed the Federal Circuit’s holding and remanded the case for further proceedings. The Court held that “when reviewing a district court’s resolution of subsidiary factual matters made in the course of its construction of a patent claim, the Federal Circuit must apply a “clear error,” not a de novo, standard of review.” In the opinion penned by Justice Breyer, the Court reasoned that Federal Rule of Civil Procedure 52(a)(6) mandates that an appellate court give substantial deference to district court fact finding and to contravene the lower court’s factual determinations only if there was “clear error.” In addition, the Court asserted, “A district court judge who has presided over, and listened to, the entirety of a proceeding has a comparatively greater opportunity to gain that familiarity than an appeals court judge.”

The decision is significant because claim construction has become such a major component of patent litigation and because the Court of Appeals for the Federal Circuit (CAFC) has a propensity of reversing a large number of claim construction decisions. Under this ruling, determinations regarding evidence “intrinsic to the patent” will continue to be reviewed de novo on appeal. However, determinations regarding “extrinsic evidence” will now be reviewed with deference on appeal. The act of consulting a dictionary – which is how a court might determine “the meaning of a term in the relevant art during the relevant time period” – seems entitled to deference. However, this decision will serve to generate endless disputes over what is extrinsic vs. intrinsic evidence and what are isolated boundaries vs. contextual boundaries. The legal analysis is still required for claim construction which will be reviewed de novo by the CAFC. And intrinsic evidence may be viewed as determinative in claim construction by the CAFC as to retain de novo review… thus the CAFC may still have a high reversal rate for claim construction decisions and less certainty for district court decisions.