Proof of Equivalence After Festo


An accused product or process that does not literally infringe a claim may still infringe under the doctrine of equivalents if each limitation of the claim is met by the accused product or process either literally or equivalently. Cybor Corp. v. Fas Technologies, Inc., 138 F.3d 1448, 1459 (Fed. Cir. 1998) (en banc). In Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 122 S. Ct. 1831 (2002), the Supreme Court reaffirmed the vitality of the doctrine of equivalents, stating that "equivalents remain a firmly entrenched part of the settled rights protected by the patent." Id. at 1838. The Court explained that "[t]he doctrine of equivalents is premised on language's inability to capture the essence of innovation":

The language in the patent claims may not capture every nuance of the invention or describe with complete precision the range of its novelty. If patents were always interpreted by their literal terms, their value would be greatly diminished. Unimportant and insubstantial substitutes for certain elements could defeat the patent, and its value to inventors could be destroyed by simple acts of copying. For this reason, the clearest rule of patent interpretation, literalism, may conserve judicial resource but is not necessarily the most efficient rule. The scope of a patent is not limited to its literal terms but instead embraces all equivalents to the claims described.

Id. at 1837, 1839. The Court recognized that "the doctrine of equivalents renders the scope of patents less certain," but rationalized that this "uncertainty [is] the price of ensuring the appropriate incentives for innovation." Id. at 1837-38.

The doctrine of equivalents is thus the antithesis of literalism. Yet, one must first construe the literal meaning of the claim limitations to determine their equivalents. As the Supreme Court explained in Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997), "application of the doctrine of equivalents involves determining whether a particular accused product or process infringes upon the patent claim, where the claim takes the form - half express, half implied - of 'X and its equivalents.'" Id. at 35. One must construe the meaning of "X" before determining its scope of equivalents.

The Supreme Court further made clear that equivalents must be assessed on a limitation-by-limitation basis; this is the so-called All Elements Rule:

Each element contained in a patent claim is deemed material to defining the scope of the patented invention, and thus the doctrine of equivalents must be applied to individual elements of the claim, not to the invention as a whole. It is important to ensure that the application of the doctrine, even as to an individual element, is not allowed such broad play as to effectively eliminate that element in its entirety.

Id. at 29; see also Allen Eng'g Corp. v. Bartell Indus., Inc., 2002 WL 1765989 *4 (Aug. 1, 2002 Fed. Cir.).

Thus, determining infringement under the doctrine of equivalents is a two step process. First, the claim must be construed to determine its literal scope and meaning. Second, the properly construed claim must be compared with the accused product or process to determine whether all of the claim limitations are present either literally or equivalently. Allen Eng'g, 2002 WL 1765989 at *3-4. Claim construction is an issue of law for the court. Markman v. Westview Instruments, Inc., 52 F.3d 967, 976 (en banc), aff'd, 517 U.S. 370 (1996). Determination of infringement, whether literal or under the doctrine of equivalents, is a question of fact. Forest Labs., Inc. v. Abbott Labs., 239 F.3d 1305, 1310 (Fed. Cir. 2001).


"It is well-settled that, in interpreting an asserted claim, the court should look first to the intrinsic evidence of record, i.e., the patent itself, including the claims, the specification and, if in evidence, the prosecution history. . . . Such intrinsic evidence is the most significant source of the legally operative meaning of disputed claim language." Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582 (Fed. Cir. 1996) (citation omitted).

First, the court is to "look to the words of the claims themselves . . . to define the scope of the patented invention." Id. The words "are generally given their ordinary and customary meaning." Id. However, "a patentee may choose to be his own lexicographer and use terms in a manner other than their ordinary meaning, as long as the special definition of the term is clearly stated in the patent specification or file history." Id.

Second, "it is always necessary to review the specification." Id. "The specification acts as a dictionary when it expressly defines terms used in the claims or when it defines terms by implication." Id. "Claims must be read in view of the specification, of which they are a part." Id.

Third, if introduced, the prosecution history of the patent should also be considered. Allen Eng'g, 2002 WL 1765989 at *3. "The prosecution history 'is often of critical significance in determining the meaning of the claims.'" Id.

The Federal Circuit has made clear that "reliance on extrinsic evidence to interpret claims is proper only when the claim language remains genuinely ambiguous after consideration of the intrinsic evidence." Bell & Howell Document Management Prods. Co. v. Altek Sys., 132 F.3d 701, 706 (Fed. Cir. 1997); accord Vitronics, 90 F.3d at 1583. However, the Federal Circuit has also noted that technical treatises and dictionaries may be treated differently from other types of extrinsic evidence:

Although technical treatises and dictionaries fall within the category of extrinsic evidence, as they do not form a part of an integrated patent document, they are worthy of special note. Judges are free to consult such resources at any time in order to better understand the underlying technology and may also rely on dictionary definitions when construing claim terms, so long as the dictionary definition does not contradict any definition found in or ascertained by a reading of the patent documents.

Vitronics, 90 F.3d at 1584 n.6 (emphasis added).

The Federal Circuit has held that "[w]hen claims are amenable to more than one construction, they should when reasonably possible be interpreted so as to preserve their validity" Modine Mfg. Co. v. United States Int'l Trade Comm'n, 75 F.3d 1545, 1557 (Fed. Cir. 1996).


Unlike claim construction, "[i]nfringement under the doctrine of equivalents requires an intensely factual inquiry." Leggett & Platt, Inc. v. Hickory Springs Mfg. Co., 285 F.3d 1353, 1357 (Fed. Cir. 2002). Whether an accused element is equivalent to a claimed element is determined at the time of infringement, not at the time the patent issued. Warner-Jenkinson, 520 U.S. at 37.

A. The Role of Intent and Copying

Intent plays no role in determining infringement under the doctrine of equivalents. Id. at 35; Moore U.S.A., Inc. v. Standard Register Co., 229 F.3d 1091, 1107 (Fed. Cir. 2000). However, whether the alleged infringer copied the patented technology or conducted independent research or experiments may reflect on knowledge - or lack thereof - of interchangeability of substitutes of a claimed element. Warner-Jenkinson, 520 U.S. at 36. There is conflicting authority within the Federal Circuit on whether evidence of copying is relevant to infringement under the doctrine of equivalents. In Advanced Display Sys., Inc. v. Kent State Univ., 212 F.3d 1272 (Fed. Cir. 2000), the court stated that "the evidence of copying . . . supports a claim of infringement under the doctrine of equivalents." Id. at 1287. Recently, the court avowed that "[w]hile copying may be relevant to obviousness, it is of no import on the question of whether the claims of an issued patent are infringed. Indeed, the Supreme Court has specifically rejected the proposition that copying is relevant to infringement under the doctrine of...

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