Claim Construction

Rule: Each claim in a patent has a different scope. If a dependent claim adds a limitation, the independent claim is presumed not to include that limitation.

Example: Claim 1 covers a 'fastener.' Claim 2 depends from Claim 1 and adds 'wherein the fastener is a screw.' Claim 1's scope cannot be limited to screws — the doctrine presumes Claim 1 covers all fasteners.

Rule: An inventor may act as her own lexicographer and define a term differently from its ordinary meaning — but must do so 'with reasonable clarity, deliberateness, and precision' in the specification.

Example: If the specification says 'as used herein, the term "vessel" means any container for liquids,' then "vessel" in the claims has that defined meaning, not its broader ordinary meaning.

Rule: When a patent applicant makes clear and unmistakable statements distinguishing prior art during prosecution, those statements narrow the claim's scope to exclude what was disclaimed.

Example: Applicant argues 'our claimed method requires step A before step B, unlike prior art reference X which does them in any order.' The claim is now construed to require that sequence.

Rule: Claims using 'means for [function]' without reciting structure are construed to cover only the corresponding structure in the specification plus its equivalents — not all possible structures performing the function.

Example: 'means for connecting' construed to cover only the specific connector described in the spec and equivalents — not any connector that connects things.

Rule: A preamble (introductory phrase) is limiting if it gives life, meaning, and vitality to the claim. If the preamble merely states the intended use without affecting the structure or steps, it may not be limiting.

Example: 'A method of treating pain comprising...' — the preamble 'treating pain' may not be limiting if the claim body fully describes the method. But 'A pump for circulating blood' — the preamble may limit to cardiovascular pumps.

01

Identify disputed terms

Each party identifies claim terms they believe are ambiguous or have different meanings. Often 5–15 terms are disputed in a complex case.

02

Exchange claim charts

Parties exchange proposed constructions for each term. Claim charts show where each disputed term appears in the claims and specification.

03

Briefing

Opening Markman briefs, then reply briefs. Each party argues why their construction is correct under Phillips — using claim language, spec, prosecution history, and expert declarations.

04

Expert declarations

Parties submit competing expert declarations explaining how a POSITA would understand disputed terms. Experts may appear at the hearing.

05

The hearing

Attorneys argue their constructions. The judge asks questions. Unlike trial, there is no jury. Some courts allow live expert testimony; others rely on declarations alone.

06

Markman order

The court issues a written opinion defining each disputed term. This is a legal ruling reviewed de novo by the Federal Circuit (subsidiary factual findings reviewed for clear error, per Teva, 2015).

What is claim construction in patent law?

Claim construction is the legal process by which a court — or the USPTO during examination — determines the meaning and scope of patent claim terms. Because patent claims define the invention and the boundaries of patent protection, how claim terms are construed determines both infringement (is the accused product/process within the claims?) and validity (is there prior art that anticipates or renders obvious the claims as construed?). The standard: under Phillips v. AWH Corp. (Fed. Cir. 2005, en banc), claim terms are given 'the meaning that the term would have to a person of ordinary skill in the art (POSITA) in question at the time of the invention.' This is an objective standard — not what the inventor subjectively intended, and not the plain meaning from a general English dictionary. Sources of meaning — in priority order: (1) the claims themselves, read in context of the entire patent; (2) the specification (written description and drawings), which is 'the single best guide to the meaning of a disputed term'; (3) the prosecution history (what the applicant said to the USPTO); and only then, if ambiguity remains, (4) extrinsic evidence — expert testimony, technical dictionaries, treatises. Claim construction is decided by the judge (not the jury) as a matter of law — this is the Markman holding (Markman v. Westview Instruments, U.S. Supreme Court 1996). The jury then applies the construed claims to the facts.

What is the Phillips v. AWH standard for claim construction?

Phillips v. AWH Corp. (Fed. Cir. 2005, en banc) is the controlling Federal Circuit decision on how to construe patent claim terms. The Federal Circuit granted en banc review to resolve a circuit split over whether claim terms should be construed primarily from dictionaries (Texas Digital approach) or primarily from the specification (intrinsic-first approach). The court held: (1) Intrinsic evidence controls. Courts must consult claim language, the specification, and the prosecution history before any extrinsic sources. The specification is 'the single best guide to the meaning of a disputed term.' (2) Extrinsic evidence is subordinate. Dictionary definitions, expert testimony, and treatises can be consulted but cannot override clear intrinsic evidence. The Texas Digital approach of starting with dictionaries was rejected. (3) Ordinary meaning = POSITA meaning at time of invention. A claim term receives 'the meaning that the term would have to a person of ordinary skill in the pertinent art at the time of the invention.' (4) The specification informs but cannot supplant the claims. Embodiments in the specification do not limit claim scope unless the specification shows a clear disavowal of broader scope or an explicit limiting definition. (5) Claim differentiation: dependent claims create presumption that independent claims are broader. Impact: Phillips significantly increased the weight given to the specification relative to dictionary definitions, which had been the dominant approach under Texas Digital. This matters in drafting — specification language describing the invention's 'essence' or 'purpose' can inadvertently limit broader claims.

What is a Markman hearing and how does it work?

A Markman hearing (also called a claim construction hearing) is a proceeding in patent litigation where the judge — not the jury — determines the meaning of disputed claim terms before trial. The name comes from Markman v. Westview Instruments, Inc. (U.S. Supreme Court 1996), where the Court held unanimously that claim construction is a matter of law for the court, not a factual question for the jury. How it works: (1) Exchange of claim charts: each party identifies the disputed claim terms and proposes constructions; (2) Briefing: each party submits opening and reply briefs with arguments supported by intrinsic and extrinsic evidence; (3) Expert declarations: parties submit competing expert declarations on how a POSITA would understand the disputed terms; (4) Hearing: attorneys argue their constructions; the judge may ask questions; expert witnesses may appear; (5) Markman order: the judge issues a written claim construction ruling (the 'Markman order'), defining each disputed term. Why Markman hearings matter: the claim construction ruling often determines who wins the case. If a term is construed broadly, the accused product may be infringing and prior art may invalidate. If construed narrowly, infringement may be avoided and the patent survives. Studies show that claim construction rulings are reversed on appeal ~25–30% of the time (the Federal Circuit reviews claim construction de novo as a legal question — Teva Pharmaceuticals USA, Inc. v. Sandoz (U.S. 2015) introduced clear-error review for factual subsidiary findings). Many cases settle after Markman rather than proceed to trial.

How does claim construction affect infringement analysis?

Claim construction is the first step in infringement analysis — you cannot determine infringement without first knowing what the claims mean. The two-step test: (1) Construe the claims (legal question for the judge); (2) Compare the construed claims to the accused product or process (factual question for the jury or judge in bench trials). For literal infringement: every element of the claim (as construed) must be present in the accused product or process, either literally or equivalently. One missing element = no literal infringement. For the Doctrine of Equivalents (DoE): even if a claim element is not literally present, infringement may exist if the accused product performs substantially the same function, in substantially the same way, to achieve substantially the same result (function-way-result test, Graver Tank, 1950). DoE is constrained by prosecution history estoppel: if an applicant narrowed a claim during prosecution to distinguish prior art, the patent owner cannot use DoE to recapture the surrendered subject matter (Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., U.S. 2002). The importance: a broader claim construction means more accused products can be found infringing. A narrower construction may make the patent 'easier to design around' (accused infringer avoids infringement by simply avoiding the narrowly defined claim term).

How does claim construction affect patent drafting strategy?

Claim construction rules directly inform how to draft strong patent claims. Key drafting lessons from claim construction doctrine: (1) Specification language can limit claim scope — avoid describing your invention as 'the invention requires' or 'the present invention is limited to' — these phrases signal disavowal and narrow claim construction. Instead, say 'in one embodiment' or 'in one aspect.' (2) Define terms you care about. Use the lexicographer rule proactively: if you want a term to have a broader or narrower meaning than its ordinary meaning, define it explicitly in the specification. (3) Prosecution history is forever. Arguments made to distinguish prior art become permanent limitations on claim scope. Before making a narrowing argument, consider whether you can instead amend the claims — the prosecution history estoppel from an argument is generally broader than from a claim amendment. (4) Avoid specification disavowal. If every embodiment in your specification includes feature X, the court may limit your claims to include X even if the claim language doesn't require it. Include a broad embodiment or use 'optionally' language. (5) Draft independent claims first, then dependent claims — and make sure your dependent claims add limitations not present in the independent claims (or you'll lose the benefit of claim differentiation for the independent). (6) Use 'comprising' not 'consisting of' for transitional phrases — 'comprising' is open-ended (additional elements are allowed), 'consisting of' is closed (no unlisted elements). Patent prosecutors routinely consider how claims will be construed during litigation when drafting, not just how they'll be examined.