Background
Teva Pharmaceuticals held patents covering Copaxone (glatiramer acetate), a widely prescribed treatment for relapsing-remitting multiple sclerosis. Sandoz sought to market a generic version and challenged the patents, arguing that key claim terms were indefinite — specifically, the term “molecular weight” as used in the patents, which could be interpreted using several different scientific measures (peak average molecular weight, weight average molecular weight, or number average molecular weight), each yielding different values. Teva argued the patents made clear which measure was intended; Sandoz argued the patents were internally inconsistent and the claims therefore indefinite.
The district court construed the claims after a Markman hearing and found them definite, relying in part on expert testimony about how a skilled artisan would understand the claim language in the context of the specification. The district court credited Teva’s expert and concluded the patents adequately informed those skilled in the field which molecular weight measure was intended.
The Court’s Holding
The Federal Circuit reversed, applying de novo review to the district court’s claim construction — consistent with the Federal Circuit’s longstanding rule under Cybor Corp. v. FAS Technologies (1998) that claim construction receives no deference on appeal. The Federal Circuit independently reviewed the claims and specification and concluded that the patent’s use of “molecular weight” was ambiguous and indefinite, disagreeing with the district court’s interpretation. Because the Federal Circuit reviewed the underlying factual determinations (including the expert testimony about skilled artisan understanding) de novo rather than deferentially, it was able to reach a different conclusion than the district court on the same record.
Teva petitioned the Supreme Court for certiorari, arguing that de novo review of all claim construction — including the subsidiary factual findings — violated Federal Rule of Civil Procedure 52(a)(6), which requires appellate courts to review district court factual findings for clear error rather than de novo.
Key Takeaways
- Under the Federal Circuit’s 2013 ruling, all aspects of claim construction — including underlying findings about how skilled artisans would understand claim terms — received de novo appellate review with no deference to the district court.
- The Supreme Court granted certiorari and reversed in January 2015, holding that while the ultimate claim construction (a legal question) is reviewed de novo, subsidiary factual findings underlying claim construction must be reviewed for clear error under Rule 52(a)(6).
- The Supreme Court’s reversal meant Teva’s patents should survive if the district court’s factual findings supporting definiteness were not clearly erroneous — on remand, the Federal Circuit ultimately upheld the district court’s finding of definiteness.
- Post-Teva, the standard of review in claim construction appeals is bifurcated: legal conclusions (claim scope, interpretation of intrinsic evidence) are de novo; factual findings (extrinsic evidence, expert testimony about skilled artisan understanding) are reviewed for clear error.
Why It Matters
The Federal Circuit’s 2013 Teva decision represented the culmination of a debate that had persisted for over a decade about whether any deference should apply to claim construction on appeal. The court’s answer — no deference at all, even to factual findings — produced extremely high reversal rates for claim construction at the Federal Circuit, often exceeding 30-40%. This unpredictability created a major problem for patent litigants: even after winning a Markman hearing, parties faced substantial risk that the Federal Circuit would reread the claims from scratch and reach a different conclusion.
The Supreme Court’s 2015 correction restored partial deference and was intended to stabilize claim construction outcomes. In practice, the impact has been more modest than some hoped — most claim construction disputes turn on intrinsic evidence (the patent’s own claims, specification, and prosecution history), which remains subject to de novo review. But for cases involving genuine disputes about how skilled artisans would understand technical claim language — exactly the kind of dispute in Teva’s molecular weight case — the clear-error standard now provides meaningful protection for district court findings supported by credible expert testimony.