Patent Litigation · Claim Construction

The Markman Hearing

Before a patent case goes to the jury, the judge interprets what the patent claims actually mean. This “Markman hearing” often decides the entire case before trial begins.

The fundamental rule

Claim construction is a question of law for the judge — not a question of fact for the jury. This was established unanimously by the Supreme Court in Markman v. Westview Instruments, Inc. (1996) and shapes all patent litigation strategy that follows.

The origin case

Markman v. Westview Instruments (1996)

Herbert Markman patented an inventory control system for dry-cleaning stores. His patent claimed a system that tracked clothing inventory and financial transactions. Westview Instruments made a competing system that Markman claimed infringed his patent.

The dispute turned on a single word: “inventory.” Markman argued it meant clothing items. Westview argued it meant money. The trial court agreed with Westview as a matter of law; the jury had originally found infringement.

The Supreme Court held (unanimous, 1996)

Claim construction — interpreting the meaning and scope of patent claims — is a matter of law to be decided by the judge, not the jury. The Court cited the historical practice of courts (not juries) construing written legal instruments, and the need for uniformity in patent claim interpretation. Juries decide whether the facts of infringement and validity are proven; judges decide what the claims mean.

The practical consequence: every patent case now has a pretrial “Markman hearing” where the parties argue what disputed claim terms mean. The judge's ruling defines the legal playing field for the rest of the case.

How claims are construed

The Phillips hierarchy of evidence

In Phillips v. AWH Corp. (Fed. Cir. 2005) (en banc), the Federal Circuit settled the rules for claim construction evidence. Courts use a strict hierarchy:

1st — Claims

Controlling

The claims themselves define the scope. Claim construction starts with the words of the claims. Terms in one claim are often illuminated by their use in other claims — dependent claims narrow independent claims, so the independent claim must be broader.

Example

If claim 1 says 'a fastener' and claim 2 says 'the fastener of claim 1, wherein the fastener is a bolt,' then 'fastener' in claim 1 must be broader than a bolt — it cannot be limited to bolts.

2nd — Specification

Highly authoritative

The specification is 'the single best guide to the meaning of a disputed term' (Phillips). Courts read claims in light of the specification to understand how the inventor used a term. But limitations from the specification (a preferred embodiment) should not be read into the claims unless the specification defines the term.

Example

If the specification describes only one embodiment — a red widget — that does not limit the claims to red widgets unless the specification says 'the widget is red' as a definitional statement.

3rd — Prosecution History

Authoritative (limiting)

The patent's prosecution history (arguments, amendments, interviews with the examiner) can limit claim scope. If the patentee argued that the claims do not cover X, the patentee cannot later argue they do cover X. This is prosecution history estoppel.

Example

Applicant argues: 'The claim is limited to Method A, not Method B.' After the patent issues, the patentee cannot argue that the claims cover Method B.

4th — Extrinsic Evidence

Secondary (limited weight)

Dictionaries, technical treatises, expert testimony, and other external sources can be used to understand the technical field and ordinary meaning — but only if the intrinsic evidence is unclear. Extrinsic evidence cannot override clear intrinsic meaning.

Example

A technical dictionary defines 'module' in software engineering. A judge may consult this to understand the ordinary meaning if the patent does not define 'module' — but if the specification defines it, the dictionary is irrelevant.

The proceeding

How a Markman hearing is conducted

Exchange of Joint Claim Construction Chart

~3–6 months post-complaint

Parties identify disputed claim terms and exchange proposed constructions. The joint chart is filed with the court showing each disputed term, plaintiff's proposed construction, and defendant's proposed construction.

Claim Construction Briefs

Staggered — opening, opposition, reply

Each side files opening, opposition, and reply briefs arguing for their proposed constructions. Briefs rely on intrinsic evidence (claims, specification, prosecution history) and sometimes expert declarations.

Expert Declarations

Concurrent with or after briefing

Parties may submit expert declarations by technical experts (explaining what POSITA would understand claim terms to mean) or claim construction experts (a limited category). Experts can be cross-examined if the court allows live testimony.

Oral Argument / Hearing

Usually a half or full day

Counsel argue before the judge. Some judges ask extensive questions and drill into the specification; others are passive. Some courts allow tutorials (technical primers) for complex technology. Most courts do not allow live expert testimony — it is briefs-only.

Claim Construction Order

Weeks to months after hearing

The court issues its claim construction order, defining each disputed term. This order is immediately influential — the case may settle, or both sides dramatically reassess their positions. The order is appealable to the Federal Circuit de novo after final judgment.

Strategy

Strategic implications for patent owners and defendants

As the Patent owner

Draft claims with clear antecedent basis and consistent use of terminology — ambiguous terms give defendants room to argue narrow constructions
Avoid over-narrowing the specification — a specification full of 'the invention is limited to…' language can restrict claim scope at Markman
Avoid unnecessary statements during prosecution — statements distinguishing prior art can create prosecution history estoppel that limits the claim scope at Markman and in the doctrine of equivalents
Consider lexicography carefully — defining a term in the specification controls that term's meaning at Markman, for better or worse

As the Accused infringer (defendant)

Mine the prosecution history for narrowing amendments and disclaimers — these limit claim scope and can exclude the accused product
Focus on inconsistencies between different claim terms — if two claims use different words, the terms likely have different meanings (claim differentiation doctrine)
Use specification embodiments strategically — if the only embodiment described doesn't work the way the plaintiff claims, argue the claim is limited to what is described
File for inter partes review (IPR) early — IPR uses a different (broader) claim construction standard and can invalidate claims, mooting Markman entirely

FAQ

Markman hearing questions

What is a Markman hearing?

A Markman hearing (formally a 'claim construction hearing') is a pretrial proceeding in a patent infringement case where the federal judge interprets the meaning of disputed terms in the patent claims. The name comes from Markman v. Westview Instruments, Inc. (1996), in which the Supreme Court held unanimously that claim construction is a question of law for the judge — not a question of fact for the jury. Before a Markman hearing, both parties brief the court on how disputed claim terms should be interpreted. The judge hears arguments (and sometimes expert testimony) and then issues a 'claim construction order' defining each disputed term. This construction is then applied when the jury decides infringement and validity.

What evidence does a judge use to construe patent claim terms?

In Phillips v. AWH Corp. (Fed. Cir. 2005) (en banc), the Federal Circuit established the hierarchy of evidence for claim construction: (1) Intrinsic evidence — the patent itself — is primary and most important. The claims are read in light of the specification (the written description), and the prosecution history (the back-and-forth between the inventor and the USPTO during examination) is also considered. (2) Extrinsic evidence — anything outside the patent file — is secondary and less reliable. This includes dictionaries, technical treatises, expert testimony, and inventor testimony. Phillips established that intrinsic evidence controls over extrinsic evidence, and courts should not rely on extrinsic evidence to change the ordinary meaning of a term if the intrinsic evidence makes the meaning clear. Words are given their 'plain and ordinary meaning' to a person of ordinary skill in the art (POSITA) at the time of the invention, unless the patentee defined the term differently (lexicography) or disclaimed certain scope (disclaimer).

Why does the Markman hearing often decide the outcome of a patent case?

Claim construction often decides the case because it defines the scope of the patent — what the claims cover and what they do not. A broad claim construction increases the chance of finding infringement; a narrow construction may exclude the accused product entirely. For example, if a patent claim requires a 'reciprocating bale' and the judge construes it narrowly as requiring a specific mechanical motion, the defendant's product (which uses a different motion) may not infringe. If the judge had construed the term more broadly, infringement might be found. After Markman, the parties often reassess settlement values because the construction signals who will likely win on infringement and validity. Studies show that approximately 25–35% of patent cases settle shortly after claim construction orders are issued.

Can a Markman claim construction order be appealed?

Yes — and this is an important feature of patent litigation. Because claim construction is a question of law (not fact), the Federal Circuit reviews Markman orders de novo (fresh review, no deference to the trial court's interpretation). This means the Federal Circuit can — and frequently does — overturn a district court's claim construction. A 2014 Federal Circuit decision (Teva Pharmaceuticals v. Sandoz) added a limited fact-deferential review for subsidiary factual determinations that underlie claim construction, but the ultimate claim construction question remains de novo. The high reversal rate on claim construction (historically around 30–40% before Teva) makes it one of the most uncertain phases of patent litigation and a major driver of appellate review.

What is prosecution history estoppel and how does it affect claim construction?

Prosecution history estoppel limits how broadly a claim can be interpreted based on statements the applicant made to the USPTO during prosecution. If the inventor narrowed a claim (by amending it) or made representations about its scope (by arguing against a rejection) to overcome a rejection, those narrowing acts create estoppel — the patentee cannot later in litigation claim the scope they gave up during prosecution. Under Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co. (2002), a narrowing amendment that surrenders subject matter raises a presumption that the patentee surrendered all territory between the original and amended claim language for purposes of the doctrine of equivalents. Prosecution history is part of the 'intrinsic evidence' hierarchy and is reviewed at Markman to understand what the applicant disclaimed.