What is Claim Construction?
The Phillips hierarchy of intrinsic and extrinsic evidence, the Markman hearing, the difference from the USPTO's standard, and why construction usually decides infringement before trial.
Definition
Claim construction is the legal process by which a court determines the meaning and scope of the terms in a patent claim before comparing the claim to an accused product or to prior art. It is decided by the judge as a question of law, usually in a Markman hearing, and frequently determines the outcome of infringement and validity.
Key Facts
- Decided by: The judge, not the jury, under Markman v. Westview Instruments (1996)
- Governing framework: Phillips v. AWH (Fed. Cir. 2005, en banc), which ranks the sources of meaning
- Standard in court: Ordinary and customary meaning to a person of ordinary skill in the art at the time of filing, read in the context of the whole patent
- Standard at the USPTO: The same Phillips standard applies in inter partes review since 2018; during examination, the examiner uses the broadest reasonable interpretation
- Timing: Typically after initial contentions and before expert discovery, with a Markman order issued months before trial
- Appeal: Reviewed de novo, except for underlying factual findings based on extrinsic evidence, under Teva v. Sandoz (2015)
The Phillips Hierarchy
- Claim language: The words themselves, including how the same term is used in other claims; claim differentiation presumes different claims have different scope
- Specification: The single best guide; the patentee may act as its own lexicographer by defining a term, or may disavow scope by clear statements, but limitations from preferred embodiments are not imported into the claims absent such intent
- Prosecution history: Arguments and amendments made to win allowance can narrow a term; this is the same record that gives rise to prosecution history estoppel
- Extrinsic evidence: Dictionaries, treatises, and expert testimony, which may inform but cannot contradict the intrinsic record
The Markman Process
The parties exchange lists of disputed terms and proposed constructions, then file briefs, and the court holds a hearing that may include technology tutorials and expert testimony. The resulting order construes the disputed terms and often triggers summary judgment: if a claim term is construed to require a feature the accused product lacks, there is no infringement, and if it is construed broadly enough to read on the prior art, the claim is invalid. Stipulated non-infringement followed by appeal of the construction is a common path.
Special Rules
- Means-plus-function terms under § 112(f) are construed to cover the corresponding structure in the specification and its equivalents
- Terms of degree such as "about" or "substantially" are construed by reference to the specification's guidance, and are indefinite if none exists
- Preambles limit the claim only when they give life and meaning to it, for example by providing antecedent basis
- "Comprising" keeps a claim open to additional elements; "consisting of" closes it
Construction Before Litigation
Every claim chart, freedom-to-operate opinion, and licensing valuation rests on an implicit construction of the key terms. Doing it explicitly, by reading the specification and prosecution history the way a court would, is what separates a chart that survives a Markman order from one that does not. Drafting with construction in mind means defining critical terms in the specification and keeping office action arguments narrow enough not to surrender scope that the claims will need later.
Frequently Asked Questions
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What is a Markman hearing?
A pretrial hearing at which the judge hears argument, and sometimes expert testimony and technology tutorials, on the meaning of disputed claim terms and then issues an order construing them. It is named after Markman v. Westview Instruments (1996), which held that claim construction is a question of law for the court.
What evidence is used to construe patent claims?
Under Phillips v. AWH, primarily the intrinsic evidence: the claim language, the specification, and the prosecution history, in that order of weight. Extrinsic evidence such as dictionaries and expert testimony may be consulted but cannot contradict the intrinsic record.
What is the difference between claim construction in court and at the USPTO?
During examination, the examiner gives claims their broadest reasonable interpretation consistent with the specification, because the applicant can still amend. In litigation, and in inter partes review since 2018, the Phillips standard applies: the ordinary meaning to a skilled person in light of the whole patent.
Why does claim construction often decide the case?
Because both infringement and validity depend on what the claims cover. A construction that requires a feature the accused product lacks ends the infringement case; one broad enough to reach the prior art ends the validity case. Many cases settle or are resolved on summary judgment immediately after the Markman order.
Can the specification limit the claims?
Yes, when the patentee clearly defines a term or clearly disavows scope. But courts do not import limitations from the preferred embodiments into the claims merely because the specification describes only one way of practicing the invention. The line between reading claims in light of the specification and reading limitations into them is the most litigated question in construction.
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