Background
Edward Phillips held a patent on modular steel-shell panels that could be assembled into walls — specifically vandalism-resistant enclosures for correctional facilities. The patent claimed panels with internal steel baffles arranged at acute angles. AWH Corporation manufactured and sold panels it claimed did not infringe Phillips’s patent, and the parties’ dispute centered entirely on how to interpret the word “baffles” in the patent’s claims.
The district court used dictionaries as its primary tool to interpret “baffles,” arriving at a construction that favored AWH. Phillips appealed. A Federal Circuit panel affirmed, relying significantly on dictionaries. The Federal Circuit then granted rehearing en banc — taking the case before all its active judges — to resolve persistent disagreement about the proper methodology for construing patent claims. Specifically, the court wanted to address whether dictionaries should be treated as primary sources (as some prior decisions suggested) or whether the patent’s own documents should take precedence.
The case was closely watched because claim construction is the pivotal step in virtually every patent infringement case. How courts interpret patent claim terms determines the scope of the patent — what products and processes are covered — and thus the outcome of billions of dollars in patent litigation annually.
The Court’s Holding
The en banc Federal Circuit established a clear hierarchy: patent claims are primarily interpreted through intrinsic evidence — the claim language itself, the patent specification, and the prosecution history (the record of communications between the applicant and the Patent Office). Extrinsic evidence, including dictionaries, treatises, and expert testimony, may supplement but cannot override intrinsic evidence.
The court particularly emphasized the centrality of the specification — the written description of the invention that forms the body of the patent document. The specification, the court reasoned, is the single best guide to the meaning of a disputed term, because inventors chose their words to describe their inventions in their own patent documents. The court rejected the Texas Digital methodology that had elevated dictionaries to near-equal footing with the specification, holding that this approach allowed claims to be defined too broadly based on general dictionary meanings divorced from the actual invention described in the patent.
Applying these principles, the court held that “baffles” in Phillips’s patent referred to structures designed to deflect or obstruct something — not merely any structure oriented at an angle — and remanded for a new infringement determination. Judge Mayer’s partial dissent argued that the court had failed to resolve the fundamental unpredictability of claim construction, and that only a deferential standard of appellate review could cure the Federal Circuit’s high claim-construction reversal rate.
Key Takeaways
- The patent specification is the primary resource for interpreting claim terms — courts must read claims in the context of the entire patent document.
- Dictionaries and other extrinsic sources are secondary to the patent’s own intrinsic record; they may clarify meaning but cannot expand or override it.
- Prosecution history — the record of patent office proceedings — is part of the intrinsic record and can limit the scope of claims through disclaimer or argument.
- Claims should be interpreted as a person of ordinary skill in the relevant field would have understood them at the time the patent was filed.
- Phillips effectively ended the “Texas Digital” approach that had made dictionary definitions the starting point for claim construction.
Why It Matters
Phillips v. AWH is arguably the most important Federal Circuit claim construction case since Markman v. Westview Instruments (1996) established that judges, not juries, decide how patent claims are interpreted. By reanchoring claim construction in the patent’s own words and specification, Phillips made it harder for patent holders to argue for broad interpretations based on dictionary definitions, and made it harder for accused infringers to exploit ambiguous claim language. The decision shaped the entire subsequent trajectory of patent litigation strategy.
Despite Phillips, the Federal Circuit continued to reverse claim constructions at high rates, and the debate about deference and consistency that animated Judge Mayer’s dissent resurfaced a decade later when the Supreme Court addressed appellate review of claim construction in Teva Pharmaceuticals v. Sandoz (2015). For practitioners, Phillips is required reading: every patent prosecution and litigation strategy must account for how the specification will inform the interpretation of every claim word.