Background
Genuine Enabling Technology LLC owns U.S. Patent No. 6,219,730, which covers a method and system for computing using user input via a type of device described in the patent as a “voice mouse” — a device that captures signals, including voice or sound, to generate input for a computing system. The central claim term in dispute was “input signal,” which the parties construed differently: Genuine argued it meant “a signal having an audio or higher frequency,” while Nintendo argued for a much narrower construction requiring signals above 500 Hz specifically.
The district court adopted Nintendo’s 500 Hz threshold, relying heavily on extrinsic evidence — specifically, expert testimony that cited industry standards and technical references defining audio frequencies. Based on that construction, the district court granted summary judgment of noninfringement in Nintendo’s favor, reasoning that Genuine could not show Nintendo’s products generated input signals within the construed scope. Genuine appealed.
The Court’s Holding
The Federal Circuit reversed. The court reaffirmed the foundational principle that claim construction must be grounded in the intrinsic record — the patent’s claims, specification, and prosecution history — not in extrinsic evidence that introduces limitations without basis in those sources. Extrinsic evidence, including expert testimony, can help clarify the meaning of a term as a skilled artisan would understand it, but it cannot be used to impose a specific numeric boundary on a claim term when that boundary appears nowhere in the intrinsic record.
The court found that the district court had done precisely what the Federal Circuit’s precedents prohibit: it relied on “extrinsic evidence upon extrinsic evidence” — an expert citing other extrinsic sources — to draw a specific 500 Hz line in the claim scope that the patent’s own claims, specification, and prosecution history never suggested. Prosecution history showed that the applicant had disclaimed signals below the audio frequency spectrum, but that disclaimer did not establish a specific 500 Hz threshold. The correct construction, the court held, was simply “a signal having an audio or higher frequency,” without imposing any specific numerical cutoff. The case was reversed and remanded for further proceedings.
Key Takeaways
- Claim construction must be anchored in the intrinsic record — the claims, specification, and prosecution history. Extrinsic evidence supplements intrinsic sources but cannot create scope limitations that have no basis in the patent itself.
- Where the prosecution history shows a disclaimer of certain subject matter, the disclaimer is limited to what was clearly surrendered — it does not automatically import specific numerical boundaries or technical standards from outside the record.
- Relying on a chain of extrinsic evidence — an expert citing other external technical sources — to establish a precise claim limitation that the intrinsic record never mentions is error.
- District courts must be cautious when adopting expert-driven claim constructions that draw bright lines in claim scope not reflected in the patent’s own documents.
Why It Matters
Claim construction determines the scope of a patent, and the outcome of infringement suits often turns entirely on how the court defines key terms. The Federal Circuit has consistently held that the intrinsic record — the patent document itself — is the primary source for claim construction, and that extrinsic evidence plays a subordinate, clarifying role that cannot override intrinsic sources or add limitations they do not contain.
Genuine Enabling Technology v. Nintendo is a clear illustration of the limits on extrinsic evidence in claim construction. Courts that allow expert testimony to supply numeric thresholds or technical definitions that the patent’s own language does not suggest risk reversible error. For patent litigants, the ruling reinforces the importance of building claim construction arguments on the intrinsic record first — and of scrutinizing opposing constructions that depend heavily on outside technical standards or expert-driven definitions.