Center for Advanced Study & Research on Innovation Policy


CASRIP Newsletter - Fall 2005, Volume 12, Issue 2

En Banc Federal Circuit Adopted a Uniform Methodology for Claim Construction, Phillips v. AWH Corp. [1]

±By Toshiko Takenaka

On 12 July 2005, the United States Court of Appeals for the Federal Circuit issued an en banc decision in Phillips, clarifying the roles of specifications and dictionaries in interpreting patent claims.  Phillips sought to harmonize the methodology of claim interpretation after a 10 year struggle to define the metes and bounds of the patented invention since the seminal Markman decision[2]  in which the en banc Federal Circuit declared the exclusive authority of the court over issues associated with claim interpretation.[3] With an endorsement of the court's authority from the Supreme Court,[4] the en banc court confirmed in Cybor[5] its prior ruling that claim construction is a matter of pure law reviewed de novo on appeal.  Before Markman, US district courts often let juries decide the meaning of claim terms.  However, Markman forced the courts to face the challenge of applying complex patent law doctrines and interpreting technical terms with very little guidance from the Federal Circuit. 

After Markman was handed down, at first the Federal Circuit emphasized the significance of intrinsic evidence, i.e., claims, specification/drawings and the prosecution history, in interpreting claim terms, focusing on the notice function of patent claims to enhance the legal certainty.[6]  This led to a practice of discrediting the extrinsic evidence, particularly expert testimony which had been an important source for district court judges to understand the meaning of claims as would have been understood by one skilled in the art of the invention.  Heavy reliance on intrinsic evidence, particularly the specification, tended to support a narrow claim interpretation to limit to the disclosed embodiments.  To clarify the role of extrinsic evidence and avoid the impermissible practice of importing limitations into claims from the specification, the court listed situations where expert testimonies are helpful[7] and encouraged the use of dictionaries and treatises to discern the ordinary and customary meaning of claim terms before consulting intrinsic evidence.[8]  This retreat from the court's original position produced split views on the methodology of claim interpretation among Federal Circuit judges with respect to the weight given to the specification in contrast to dictionaries and introduced significant uncertainty as to the extent of patent protection.[9]

Phillips was selected to resolve this split since its technology was simple, the disputed term being "baffle".  Phillips involved a simple mechanical invention: modular steel-shell panels which can be welded together to form vandalism-resistant walls.  The term "baffle" was used to describe an element extending inwardly from the steel shell panels, but the specification did not include any detailed description of its structure.  Because the district court concluded that "load bearing means", of which "baffle" was a part, was drafted in a mean-plus-function format, it applied §112¶ 6[10]  and interpreted "baffle" to require extending at an angle other than 90 degrees to the wall faces.[11] On appeal, a three-judge panel of the Federal Circuit found that "baffle" was a structural limitation and thus found error the district court's application of  §112¶ 6 to the disputed term.[12]

Nevertheless, two judges of the panel upheld the district court's claim construction to limit "baffle" by the angle because the specification repeatedly referred to the projectile deflection ability.  Since only structures extending at acute or obtuse angles could deflect projectiles, and because the specification did not include any structure extending at 90 degrees, the panel concluded that "baffle" was limited to structures extending at angles other than 90 degrees.  One judge dissented, arguing that the majority improperly limited the term "baffle" to the embodiments disclosed in the specification instead of adopting the plain meaning of "baffle" found in a dictionary.[13]

Granting the motion for rehearing the case en banc, the Federal Circuit posed questions regarding the methodology of claim construction, on which recent decisions highlighted the different approaches taken by the Federal Circuit judges, and urged the patent community to submit their views.[14]   Such questions included: (1) should specification be given priority over dictionaries and, if so, what role should dictionaries have? (2)should courts be permitted to construe claim language narrowly for the sole purpose of sustaining validity? (3) what role should be given to expert testimonies and prosecution history? and  (4) should any aspect of trial court claim construction rulings be given deference on appeal? 

These questions were in response to an outcry from district courts and the patent community for the need to set a bright line rule.  However, the en banc court did not give such a rule but rather encouraged a case-by-case approach, while generally according priority to intrinsic evidence, including the specification, over the extrinsic evidence such as dictionaries. [15]  The en banc court reemphasized the fundamental rule that a patent claim's terms define the extent of its exclusive right.[16] The court further explained that such terms are given their ordinary and customary meaning, that which the term would have to a person skilled in the art in question at the time of the invention, i.e., as of the effective date of the patent application.[17]  To find such meaning, the court should resort to the specification because the skilled person is deemed to read the claim terms in the context of the entire patent, including the specification.[18]  Accordingly, in answering questions (1) and (3), the court emphasized the importance of all intrinsic evidence, including claims other than the disputed claims, specification/drawings and prosecution history, while discounting the significance of extrinsic evidence.  Although the en banc court did not exclude a possible use of extrinsic evidence, it cautioned against its use, citing reasons why extrinsic evidence is less reliable than intrinsic evidence because of the following reasons: (a) unlike intrinsic evidence, extrinsic evidence was not prepared with a view to explaining the patent's scope and meaning at the time of prosecution; (b) extrinsic publications, unlike claims, are not necessarily written for a hypothetical skilled person in the art; (c) extrinsic evidence consisting of expert testimony, being prepared for litigation, is very likely to suffer from bias; (d) the unbounded scope of potential extrinsic evidence makes it difficult for the court to filter useful evidence and (e) undue reliance on extrinsic evidence undermines the public notice function of patents.[19] 

The en banc court acknowledged the need to avoid impermissible importation of limitations which led to the development of the Texas Digital line of cases in which a heavy reliance was given to definitions of dictionaries.[20] It found the methodology employed in those cases inappropriate since it gave too little weight to intrinsic evidence.[21]  According to the en banc court, even if the court relies on intrinsic evidence for claim construction, it should be able to avoid impermissible importation of limitations if it keeps in mind the purpose of the specification aside from that of claim terms: to teach the best mode and enable the patented invention.[22]

Regarding question (2) the court retained the doctrine that the claims should be construed in such a manner as to preserve their validity but limited the use of the doctrine as a last resort for cases where the claim terms remain ambiguous after consulting all available sources for claim construction.[23]  The court reasoned that the PTO would not have issued an invalid patent, and thus that the ambiguity in the claim term should be resolved to sustain the validity of the patent.[24]  If resorting to other sources removes ambiguity, the doctrine plays no role in opting for one of two possible constructions, one of which would sustain the validity while the other would not.  Finally, the en banc court decided not to address question (4).[25]

In following the clarified methodology, the majority of the en banc court nevertheless found it wrong to exclude from the term "baffle" a structure oriented at a right angle, thus reversing the district court's claim construction ruling.  Instead, the en banc court adopted a construction such that a "baffle" must be a load-bearing object that serves to check, impede or obstruct flow.[26]  The court relied on the claim differentiation doctrine, explaining that the district court's interpretation, which limited "baffle" based on projectile deflection, made redundant the other claims which included specific limitations of the projectile deflection function.  This interpretation is also supported by the specification, which recites multiple functions of the baffles other than the projectile deflection. 

Two judges dissented from the reversal of claim interpretation ruling although they followed exactly the same methodology.[27]  For them, a hypothetical person skilled in the art of patented invention should have acknowledged the presence of inherent angle limitation within the term "baffle" in light of the specification which contains no disclosure of baffles at right angles and repeatedly refers to the projectile deflection function of the baffles.  Ironically, this disagreement on the inherent limitation highlighted the difficulty in setting the line between impermissible importation of limitations and permissible claim construction.

In essence, the impact of Phillips is to limit the significance of a dictionary definition, which was emphasized by the Texas Digital line of cases and to move the case law back to the status quo when Markman was decided in 1996.  However, it is very unlikely that harmonization of the methodology and reference sources can completely remove the difference with respect to the extent of patent protection resulting from claim construction.  The weight given to legal certainty encourages an abstraction from the specification instead of the claim terms and keeps the level of abstraction low in excluding the accused embodiment that is different from the embodiments disclosed in the specification.  In contrast, the weight given to the fair protection allows an abstraction from the claim terms and adopts a high level of abstraction to include variations from the embodiments in the specification and including the accused embodiment. 

Judges try to balance the competing patent policies of fair protection and legal certainty when they interpret claim terms to decide the extent of patent protection.  Depending on the weight given to the competing patent policies, the extent differs from one judge to another as is well illustrated by the dissenting judges' view with respect to the meaning of "baffle."  As a result, a perfect uniformity in claim construction and legal certainty in patent protection are impossible and unnecessary as long as judges clarify the meaning of claim terms on a case-by-case basis through case law developments.

A more detailed analysis of Phillips from the comparative law perspective can be found in Toshiko Takenaka, Claim Construction and the Extent of Patent Protection: A Comparative Analysis of the Phillips en banc Federal Circuit decision, J of Intellectual Property Law & Practice, Vol. 1, Issue 2, available on line at:

[1] Phillips v AWH Corp.,415 F.3d 1303, 75 USPQ.2d 1321 (Fed. Cir. 2005).

± Toshiko Takenaka is the Director of the Center for Advanced Study & Research on Intellectual Property, the Associate Director for the Intellectual Property Law and Policy LL.M. Program, and a Washington Research Foundation/W. Hunter Simpson Professor of Law at the University of Washington School of Law.

[2] Markman v Westview Instruments, Inc., 52 F.3d 967, 34 USPQ2d 1321 (Fed. Cir. 1995).

[3] For a discussion on the background of Phillips see Timothy R. Holbrook, Substantive Versus Process-Based Formalism in Claim Construction, 9 Lewis & Clark L. Rev. 123 (2005).

[4] Markman v Westview Instruments, 517 US 370 (1996).

[5] Cybor Corp. v FAS Techs., Inc., 138 F.3d 1448, 1451 (Fed. Cir. 1998).

[6] Vitronics Corp. v Conceptronic, Inc., 90 F.3d 1576, 39 USPQ 1573 (Fed. Cir. 1996).

[7] Pitney Bowes, Inc. v Hewlett-Packard Co., 182 F.3d 1298, 51 USPQ2d  1161 (Fed. Cir. 1999)

[8] Tex. Digital Sys. v Telegenix, Inc., 308 F.3d 1193, 64 USPQ2d 1812 (Fed. Cir. 2002)

[9]US scholars extensively criticized the confusion resulting from the different views taken by Federal Circuit judges, see, e.g., R. Polk Wagner and Lee Petherbridge, Is the Federal Circuit Succeeding? An Empirical Assessment of Judicial Performance, 152 U. Pa. L. Rev. 1105, 1111 (2004); Craig Allen Nard, Process Considerations in the Age of Markman and Mantras, 2001 U. Ill. L. Rev. 355; Craig Allan Nard, A Theory of Claim Interpretation, 14 Harv. J.L. & Tech. 1 (2000); John F. Duffy, On Improving the Legal Process of Claim Interpretation: Administrative Alternatives, 2 Wash. U. J.L. & Pol'y 109, 130-31 (2000).

[10] 35 USC §112¶ 6

[11] Phillips v AWH Corp., 2002 US Dist. LEXIS 27298 (D. Colo. Nov. 20, 2002)

[12] Phillips v AWH Corp., 363 F.3d 1207, 70 USPQ 2d 1417 (Fed. Cir. 2004).  This opinion was withdrawn by the court when the court granted rehearing the case en banc.

[13] Phillips v AWH Corp., 363 F.3d at 1216 (Dyk, J. dissenting).

[14] Phillips v AWH Corp., 376 F.3d 1382, 71 USPQ2d  1765  (Fed. Cir. 2004).

[15] Phillips v AWH Corp., 415 F.3d 1303, 75 USPQ.2d 1321 (Fed. Cir. 2005).

[16] Phillips, 415 F. 3d, at 1312, citing Innova/Pure Water, Inc. v Safari Water Filtration Sys., 381 F.3d 1111, 72 USPQ2d 1001 (Fed. Cir. 2004).

[17] Phillips, 415 F. 3d,  at 1312, citing Vitronics Corp. v Conceptronic, Inc., 90 F.3d at 1582(Fed. Cir. 1996); Innova/Pure Water, Inc. v Safari Water Filtration Sys., 381 F.3d at 1116.

[18] Phillips, 415 F. 3d,  at 1313, citing Multiform Desiccants, Inc. v Medzam Ltd., 133 F.3d 1473, 45 USPQ2d 1429 (Fed. Cir. 1998).

[19] Phillips,415 F. 3d,  at 1318.

[20] Tex. Digital Sys. v Telegenix, Inc., 308 F.3d 1193, 2002 , 64 USPQ2d 1812 (Fed. Cir. 2002).  Other cases include: CCS Fitness, Inc. v Brunswick Corp., 288 F.3d 1359, 62 USPQ2d 1658 (Fed. Cir. 2002); Nystrom v Trex Co., 374 F.3d 1105, 71 USPQ2d 1241 (Fed. Cir. 2004).

[21] Phillips, 415 F. 3d,  at 1320.

[22] Phillips, 415 F. 3d,  at 1323-24. (page 13)

[23] Phillips, __ F. 3d,  at 1327,, citing Liebel-Flarsheim Co. v Medrad, Inc., 358 F.3d 898, 69 USPQ2d 1801 (Fed. Cir. 2004).

[24] Phillips, 415 F. 3d,  at 1327, citing Klein v Russell, 86 US (19 Wall.) 433, 466, 22 L. Ed. 116 (1873).

[25] Phillips, 415 F. 3d,  at 1328.

[26] Phillips, 415F. 3d,  at 1324.

[27] Phillips, 415 F. 3d,  at 1328 (Lourie, J. , dissenting).

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