Edward Phillips owned a patent covering modular steel wall panels designed to be resistant to vandalism and projectiles. The panels used internal steel "baffles" welded to the outer shell to strengthen the structure and, as described in the specification, to help deflect bullets or other projectiles. Phillips sued AWH Corporation and related entities alleging that their wall systems infringed the patent. The district court construed the claim term "baffles" narrowly to mean structures oriented at acute angles relative to the wall face for the purpose of deflecting projectiles, based largely on descriptive passages in the specification. Under that construction, the court granted summary judgment of noninfringement because AWH's internal structures were oriented differently (e.g., at or about 90 degrees) and did not perform deflection in the same manner. A Federal Circuit panel initially affirmed in part, but the court granted rehearing en banc to clarify the proper methodology for claim construction and to review whether the district court improperly imported a limitation from the specification into the claims.
How should courts properly construe patent claim terms—specifically, whether the term "baffles" should be limited to angled, projectile-deflecting structures based on the specification—and, more generally, what evidentiary sources and hierarchy govern claim construction?
Claim terms are given their ordinary and customary meaning as understood by a person of ordinary skill in the art at the time of the invention, read in the context of the entire patent. The intrinsic record—the claims, the specification, and the prosecution history—is the primary and most reliable guide to meaning. The specification is usually the best source for understanding claim scope, but courts must not import limitations from embodiments into the claims absent clear language, express definitions (lexicography), or unmistakable disavowal. Prosecution history may inform the meaning and limit scope through clear and unmistakable disclaimer. Extrinsic evidence, including dictionaries and expert testimony, may be considered to educate the court but carries less weight and cannot contradict the intrinsic record. Claim differentiation may support broader readings but is a guide, not an absolute rule. At the time of Phillips, claim construction was treated as a question of law reviewed de novo on appeal.
The Federal Circuit (en banc) held that intrinsic evidence, especially the specification, is the primary guide to claim meaning and rejected approaches that give dictionaries primacy. Applying that framework, the court concluded that the term "baffles" was not limited to structures oriented at acute angles solely to deflect projectiles; nothing in the claims or specification clearly required that limitation, and the presence of dependent claims specifying angular ranges counseled against reading such a restriction into the independent claims. The court vacated the judgment of noninfringement and remanded for further proceedings under the proper construction.
The court explained that dictionaries cannot be the starting point or trump the context provided by the patent document. The ordinary meaning of a term arises from how a person of ordinary skill in the art would understand it in the context of the claims and the specification. The specification is highly relevant because it describes the invention and may reveal whether the patentee used a term idiosyncratically or intended particular limitations. However, the court cautioned that repeated description of a preferred embodiment does not, without more, confine claim scope; express definitions and clear, unmistakable disavowals are required to narrow claims beyond their ordinary meaning. The prosecution history can reinforce or limit meaning through applicant statements, but ambiguous statements are insufficient to create a disclaimer. Turning to the term "baffles," the court observed that the specification discussed deflecting projectiles as a purpose and benefit, but the claims themselves did not require a particular angular orientation or deflection function. Nothing in the intrinsic record showed that the patentee acted as his own lexicographer to define "baffles" exclusively as angled deflectors, nor did the prosecution history contain a clear disavowal. Moreover, dependent claims specifically recited baffles at certain angular ranges, supporting an inference under claim differentiation that the independent claims were not so limited. While dictionary definitions that describe a baffle as something that obstructs or impedes may be informative, they cannot override the contextual reading of the patent. Accordingly, the district court erred by importing an angled-orientation limitation from the specification into the claim term. The court also reiterated that extrinsic evidence, including expert testimony and dictionaries, may be considered to aid understanding but should not displace the intrinsic record. Finally, while some judges advocated revisiting appellate deference to district court fact-finding, the en banc court applied existing precedent treating claim construction as a legal issue reviewed de novo.
Phillips is the definitive framework for claim construction: it reaffirms the primacy of intrinsic evidence and cabins the use of dictionaries and other extrinsic materials. It harmonizes earlier cases, curbing the Texas Digital approach that prioritized dictionary definitions, and clarifies when and how to read limitations from the specification (rarely) and how claim differentiation, lexicography, and prosecution disclaimer operate. For law students, it is essential to understanding how courts translate technical patent language into enforceable rights and how drafting and prosecution choices affect scope. The case also anchors later developments, including Supreme Court decisions on the standard of review for subsidiary factual findings in claim construction.
Phillips v. AWH Corp. recalibrated claim construction by emphasizing that the meaning of patent claims must emerge first and foremost from the patent itself. It provides a clear hierarchy—claims, specification, prosecution history, then extrinsic evidence—that respects how a person of ordinary skill would read the patent and minimizes distortions from acontextual dictionary usage.