What Is Claim Construction?

Claim construction is the judge's ruling on what disputed patent claim words mean. Before a jury compares a product with a patent, the judge decides the meaning of the terms that matter to infringement or validity. That ruling, called claim construction or a Markman ruling, often decides the case: a broad reading helps the patent owner prove infringement but exposes the claim to prior art, and a narrow reading does the reverse. Claim construction is for the judge, not the jury (Markman v. Westview Instruments, Inc., 517 U.S. 370 (1996)). If the parties actually dispute the scope of a term that matters, the court must resolve the dispute; leaving it to the jury is error.

Claim terms carry their ordinary and customary meaning to a person of ordinary skill in the art at the time of the invention, read in the context of the entire patent (Phillips v. AWH Corp., 415 F.3d 1303 (Fed. Cir. 2005) (en banc)). The sources, in order of weight, are the claims themselves, the specification (usually the single best guide), the prosecution history, and extrinsic evidence such as dictionaries, treatises, and expert testimony, which is less reliable and cannot contradict the intrinsic record. The ordinary meaning controls unless the patentee acted as its own lexicographer by clearly defining a term, or clearly disavowed claim scope. A claim element stated as a means or step for performing a function, without reciting structure, covers only the corresponding structure described in the specification and its equivalents (35 U.S.C. § 112(f)), and a term that lacks reasonable certainty is invalid as indefinite (§ 112(b)). The ruling cannot ordinarily be appealed right away; the Federal Circuit reviews the construction de novo but defers to factual findings about extrinsic evidence (Teva Pharms. USA, Inc. v. Sandoz, Inc., 574 U.S. 318 (2015)). The Patent Trial and Appeal Board applies the same standard in post-grant proceedings (37 C.F.R. § 42.100(b)).

This term also appears as a short entry in the 36-term patent glossary in "Patent Basics for Litigation, with a Glossary." This page is the fuller treatment and links to that guide.

Pinpoint: 35 U.S.C. § 112(b), (f); Markman v. Westview Instruments, Inc., 517 U.S. 370 (1996). Related term: Claim Construction.

Sources.

• 35 U.S.C. § 112: specification, including definiteness (§ 112(b)) and means-plus-function claiming (§ 112(f)). law.cornell.edu

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