Claim Construction
What happens when expert testimony collides with the intrinsic record under Phillips v. AWH — and why district courts like Zimmer v. Howmedica Osteonics give the claims and specification the final word.
How District Courts Apply Phillips When Intrinsic Evidence Conflicts With Expert Testimony
Claim terms take their meaning primarily from the intrinsic record — the claims, the specification, and the prosecution history — not from what a party's expert says they mean. Phillips v. AWH Corp., 415 F.3d 1303 (Fed. Cir. 2005) (en banc) ranks the sources of meaning: the specification is "always highly relevant" — "[u]sually, it is dispositive; it is the single best guide to the meaning of a disputed term" — while extrinsic evidence is "less significant than the intrinsic record in determining the legally operative meaning of claim language." For outright conflicts, the en banc court left no ambiguity: a court "should discount any expert testimony that is clearly at odds with the claim construction mandated by the claims themselves, the written description, and the prosecution history."
District courts read that directive as a rule of precedence, not an invitation to weigh the two sides evenly. When an expert's definition collides with the written record, "the intrinsic evidence must take precedence when there is a conflicting definition," and "expert testimony that is clearly at odds with the intrinsic record must be discounted." Zimmer Technology, Inc. v. Howmedica Osteonics Corp., 397 F. Supp. 2d 974 (N.D. Ind. 2005) — construing claims on remand from the Federal Circuit — still preserved a role for experts in explaining the technology and clarifying how a skilled artisan would read a term, while cautioning that "less weight should be given to testimony that consists of conclusory statements or that is offered in a form not subject to cross-examination."
Reliability supplies a second route to the same result: "[e]xtrinsic evidence is less reliable than intrinsic evidence in determining the construction of claim terms, and therefore the court should discount any expert evidence that is at odds with the intrinsic evidence" — and "conclusory, unsupported assertions by experts as to the definition of a claim term are not useful to a court." HR Technology, Inc. v. Imura International U.S.A., Inc., No. 2:08-cv-02220 (D. Kan. 2009).
Recent decisions hold the line. Courts "give primacy to intrinsic evidence" and resort to extrinsic evidence only where it is "consistent with intrinsic evidence." Allele Biotechnology and Pharmaceuticals, Inc. v. Regeneron Pharmaceuticals, Inc., No. 7:20-cv-08255 (S.D.N.Y. 2022) (quoting Phillips' directive to "discount any expert testimony that is clearly at odds with the claim construction mandated by the claims themselves, the written description, and the prosecution history").
The Federal Circuit polices the hierarchy from above. Parkervision, Inc. v. Qualcomm Incorporated, 116 F.4th 1345 (Fed. Cir. 2024) vacated a summary judgment of non-infringement because the district court had "relied principally on extrinsic evidence, particularly Qualcomm's expert opinion," rather than assessing claim scope through the Phillips process — a reminder that "[e]xtrinsic evidence may not be used to contradict claim meaning that is unambiguous in light of the intrinsic evidence."
Expert testimony therefore keeps a legitimate but bounded role. It can educate the court on the technology and confirm that a proposed construction matches how a person of ordinary skill would read the term; it cannot supply a meaning the written record forecloses. When the two conflict, district courts resolve claim meaning on the intrinsic record, and expert opinions that contradict it are discounted or disregarded — not balanced against it.