Chapter §15.03 Evidentiary Hierarchy for Claim Interpretation

JurisdictionUnited States

§15.03 Evidentiary Hierarchy for Claim Interpretation

In the aftermath of Markman, the Federal Circuit has developed a robust jurisprudence addressing what evidentiary sources should be relied on to interpret patent claims. The foundational case is Vitronics Corp. v. Conceptronic, Inc.77 The Federal Circuit in Vitronics established a hierarchy of claim interpretational tools that distinguishes between "intrinsic" and "extrinsic" evidence.

[A] Intrinsic Evidence

Intrinsic evidence is that which is part of the public record associated with a patent's issuance: the patent itself and its prosecution history,78 including the prior art cited therein.79 Competitors have access to this information as soon as the patent issues, if not before,80 and it is not considered litigation-influenced.

[B] Extrinsic Evidence

Extrinsic evidence is evidence outside the official administrative record of the patent's procurement, such as testimony by technical and legal experts and testimony by the inventor. Because extrinsic evidence is not necessarily available to the public when a patent issues, and because it may be litigation-influenced, extrinsic evidence is assigned a lower status in the evidentiary hierarchy for patent claim interpretation than intrinsic evidence.

Although literally extrinsic to the official administrative record, some Federal Circuit judges questioned whether dictionaries are properly classified as extrinsic evidence. The Federal Circuit opined in a 2001 decision that dictionaries hold a "special place" and "may sometimes be considered along with the intrinsic evidence when determining the ordinary meaning of claim terms."81 In a 2002 decision the court went further, expressing the following view:

As resources and references to inform and aid courts and judges in the understanding of technology and terminology, it is entirely proper for both trial and appellate judges to consult these materials at any stage of a litigation, regardless of whether they have been offered by a party in evidence or not. Thus, categorizing them as "extrinsic evidence" or even a "special form of extrinsic evidence" is misplaced and does not inform the analysis. 82

Despite the tenor of these Federal Circuit decisions that dictionaries, encyclopedias, and treatises that were available at the time a patent was procured should be treated as intrinsic evidence, the en banc court clarified in 2005 that dictionaries are extrinsic evidence.83 As such they may be useful construction tools, but they are not assigned primary importance in the evidentiary hierarchy for patent claim interpretation.

Although extrinsic evidence is not viewed as critical or primary to claim interpretation as intrinsic evidence, this is not to say that extrinsic evidence is inadmissible or irrelevant. It is not error for a district court to rely on extrinsic evidence in construing claim terms when such evidence supports an interpretation consistent with that revealed by the intrinsic evidence. For example, in Aventis Pharma S.A. v. Hospira, Inc.,84 the Federal Circuit rejected the argument of patentees Aventis Pharma S.A. and Sanofi-Aventis U.S., L.L.C. (collectively "Sanofi") that

the district court improperly relied on extrinsic evidence in the form of expert testimony in construing th[e] claim term ["perfusion"]. According to Sanofi, because the intrinsic evidence alone dictates the proper construction of perfusion, any extrinsic evidence is irrelevant. A district court, however, has the discretion to take expert testimony into account in determining the ordinary meaning of a claim term to one skilled in the art. Phillips, 415 F.3d at 1319 ("[B]ecause extrinsic evidence can help educate the court regarding the field of the invention and can help the court determine what a person of ordinary skill in the art would understand claim terms to mean, it is permissible for the district court in its sound discretion to admit and use such evidence."). Here, the district court heard testimony from both sides' experts, including testimony from Sanofi's expert, . . . which was consistent with the intrinsic evidence and supports the conclusion that the ordinary meaning of a perfusion does not include the stability limitation proposed by Sanofi. Consequently, the district court did not err in relying on extrinsic evidence in construing this claim term. 85

[C] "Contextualist" Versus "Literalist" Approaches

Decisions of the Federal Circuit issued between 2002 and 2005 demonstrated a sharp divergence in approaches to patent claim interpretation. The Circuit judges appeared to have aligned themselves in two schools of thought on the issue: the "contextualist" and "literalist" viewpoints.86 This divergence of interpretational methodologies led the court in 2004 to call for an en banc referendum on patent claim interpretation.87 The basis of the dispute can be summarized as follows.

Federal Circuit judges who espoused the contextualist approach88 sought the "felt meaning" of patent claim terms in the context of the invention described in the patent specification. They viewed the written description and drawings of the patent as the primary tool for discerning what terms in the patent's claims mean. Contextualist judges "look to the specification 'to ascertain the meaning of a claim term as it is used by the inventor in the context of the entirety of his invention.' "89 The ordinary meaning of a term in a claim "must be considered in view of the intrinsic evidence: the claims, the specification, and the prosecution history."90 This is the traditional approach to patent claim interpretation generally followed by the Federal Circuit in its decisions prior to 2002. Despite some detours thereafter, the contextualist approach continues to carry strong weight in more recent Federal Circuit decisions.91

In contrast, Federal Circuit judges in the literalist school92 took as their lodestar the court's 2002 decision in Texas Digital Sys. v. Telegenix, Inc.93 In accordance with that decision, the literalist judges engaged in a "heavy presumption" that claim terms carry the "ordinary and customary" meaning that a person having ordinary skill in the art (PHOSITA) would attribute to them. To discern this meaning the literalist judges typically consulted definitions in dictionaries, technical treatises, and other evidentiary sources extrinsic to the patent itself.94 Indeed, Texas Digital instructed that in construing patent claims, courts should consult the dictionary before turning to a patent's written description and drawings.95 The ordinary and customary meaning as gleaned from dictionaries would be trumped only when a patent's written description or its prosecution history showed that the patentee was her "own lexicographer" in providing an explicit definition for a claim term, or had otherwise clearly disclaimed or disavowed the ordinary and customary meaning.

The April 2004 decision of a Federal Circuit panel in Phillips v. AWH Corp.96 exemplified the burgeoning conflict between the "literalist" and "contextualist" claim interpretation approaches. Phillips' patent was directed to modular, vandalism-resistant wall panels useful in building prisons and security institutions.97 The parties disputed the meaning of "baffle" in the asserted patent claim, which recited in part, "means disposed inside the [outer] shell for increasing its load bearing capacity comprising internal steel baffles extending inwardly from the steel shell walls." The Phillips panel majority affirmed the district court's reading of "baffle" as limited by the patent's specification to baffles that are oriented at acute...

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