Informal Deference: A Historical, Empirical, and Normative Analysis of Patent Claim Construction

84 Pages Posted: 22 Sep 2012 Last revised: 28 Mar 2017

See all articles by Jonas Anderson

Jonas Anderson

University of Utah - S.J. Quinney College of Law

Peter S. Menell

UC Berkeley School of Law

Date Written: September 3, 2013


Patent scope plays a central role in the operation of the patent system, making patent claim construction a critical aspect of just about every patent litigation. With the resurgence of patent jury trials in the 1980s, the allocation of responsibility for interpreting patent claims between trial judge and jury emerged as a salient issue. While the Supreme Court’s Markman decision usefully removed claim construction from the black box of jury deliberations notwithstanding its "mongrel" mixed fact/law character, the Federal Circuit's adherence to the view that claim construction is a pure question of law subject to de novo appellate review produced an unusually high reversal rate, distorting the evidentiary foundation of claim construction determinations, delaying settlement of patent cases, running up litigation costs, and turning appellate review of nearly every patent case into re-litigation of patent claim terms.

In 2004, the Federal Circuit undertook to reassess this regime in the Phillips case. The majority en banc opinion largely stayed the course. Indeed, the empirical studies to have emerged since Phillips suggest that not much has changed, finding that the reversal rate remained high and that the Federal Circuit's analytical framework remained largely unchanged. This article presents the results of a comprehensive empirical analysis of the Federal Circuit's claim construction jurisprudence from 2000 through 2011. In contrast to prior analyses, we find that the claim construction reversal rate has dropped precipitously since the Phillips decision from 37.6% to 23.8% on a per claim term basis. Reversal rates have fallen for all members of the Federal Circuit and across all technology fields except business methods. During 2011, the average reversal rate dipped to 17%.

This does not mean, however, that the problems of de novo review have been adequately resolved. So long as the Federal Circuit clings to the view that claim construction is a question of law subject to de novo review, district courts will downplay their resort to experts and fact-finding in managing claim construction. This will undermine the quality of adjudication and appellate review by failing to elicit relevant evidence and perpetuating opaque analysis and reasoning. We propose a "mongrel" standard of appellate review of claim construction decisions that better reflects the comparative strengths of trial judges in determining how skilled artisans understand patent claim terms. Formal recognition of this more deferential standard promises to improve the quality of claim construction at the trial court level while improving transparency and encouraging earlier settlement of patent disputes.

Keywords: Patent, Claim Construction, Appellate Review, Patent Scope

JEL Classification: K19, O33, O34

Suggested Citation

Anderson, Jonas and Menell, Peter S., Informal Deference: A Historical, Empirical, and Normative Analysis of Patent Claim Construction (September 3, 2013). 108 Northwestern University Law Review 1 (2014), Available at SSRN: or

Jonas Anderson

University of Utah - S.J. Quinney College of Law ( email )

383 S. University Street
Salt Lake City, UT 84112-0730
United States

Peter S. Menell (Contact Author)

UC Berkeley School of Law ( email )

2240 Bancroft Way
Berkeley, CA 94720-7200
United States

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