Vague Claim Construction Rules Lead to Reversals

A recently issued Federal Circuit decision illustrates how vague many claim construction rules can be. Storage Tech. Corp. v. Cisco Systems, Inc., 329 F.3d 823 (Fed. Cir. 2003), found that a trial court that hears many patent cases, the Northern District of California, committed several errors construing the term “caching policy identification information” in a patent covering data communication networks.

First, the trial court improperly read the preamble of the claim as a limitation, rather than merely a reference to the invention as a whole. But the Federal Circuit acknowledged there is no clear rule concerning when the preamble will properly function as a limitation: “Whether to treat a preamble as a claim limitation is determined on the facts of each case in light of the claim as a whole and the invention described in the patent.”

Second, making a common mistake, the district court relied on the specification and the prosecution history to read an additional limitation into the claims. But these materials are appropriately used to construe, rather than limit, the language of the claims. As the Federal Circuit conceded, “there is sometimes a fine line between reading a claim in light of the written description and relevant prosecution history, and reading a new limitation into the claim.” It found that the trial court had erroneously relied on an “inaccurate” statement in the prosecution history to limit the claims ' noting that an “inaccurate statement cannot override the claim language itself, which controls the bounds of the claim.” But, when is the prosecution history “inaccurate,” and when does it actually help the court to understand the meaning of the claims?

Third, the district court improperly used “extrinsic evidence” ' evidence outside the “intrinsic evidence” of the patent text and prosecution history ' to construe the claims. Extrinsic evidence is “appropriate only when an ambiguity remains after consulting the intrinsic evidence of record.” Again, however, it is not always easy to decide when the technical language of a patent is “ambiguous” enough to allow use of extrinsic evidence. Indeed, extrinsic evidence typically must be used to understand the meaning of technical terms of art used in the claims.

And these are far from the only ambiguous rules of claim construction. Consider the canon that “claim language generally carries the ordinary meaning of the words in their normal usage in the field of invention.” As the Federal Circuit recently said, “while this 'ordinary meaning' rule is usually expressed as a pat formula, the context supplied by the field of invention, the prior art, and the understanding of skilled artisans generally is key to discerning the normal usage of words in any claim.” Invitrogen Corp. v. Biocrest Mfg., L.P., 327 F3d 1364, 1367 (Fed. Cir. 2003). Clearly, there is ample room for debate about the “ordinary meaning” of a term in this context.

Is there a way to reverse the high reversal rate of claim construction rulings, without imposing a set of rules so rigid and desiccated that they do violence to the “true” meaning of patent claims? Unless the Federal Circuit decides to change the de novo review standard of Cybor and give deference to district court claim construction, it is hard to see how.

This article originally appeared in the New York Law Journal, an American Lawyer Media publication.

Why can't federal trial judges figure out what patents mean? As it held en banc in Cybor Corp. v. FAS Technologies, Inc., 138 F3d 1448 (Fed. Cir. 1998), district court rulings on claim construction ' interpretations of the meaning of patent claims ' are reviewed de novo as questions of law by the U.S. Court of Appeals for the Federal Circuit. A recent study concluded that more than 40% of all claim construction rulings reviewed by the Federal Circuit in 2001 were reversed in whole or part. Andrew T. Zidel, “Patent Claim Construction in the Trial Courts: A Study Showing the Need for Clear Guidance from the Federal Circuit,” 33 Seton Hall L. Rev. 711 (2003). While other studies have reported lower numbers, this percentage is in line with a survey cited in Judge Rader's dissenting opinion in Cybor. Judge Randall R. Rader wrote then that a “reversal rate, hovering near 50%, is the worst possible. Even a rate that was much higher would provide greater certainty.”

Claim construction isn't easy ' particularly for a non-scientist ' and trial judges will never accumulate the patent law experience of judges on the Federal Circuit. Beyond these issues, however, are the Federal Circuit's rules of claim construction too confusing? Does the Federal Circuit tinker too much with lower court rulings, like a senior lawyer who rewrites everything he receives from an associate?

An Example

A recently issued Federal Circuit decision illustrates how vague many claim construction rules can be. Storage Tech. Corp. v. Cisco Systems, Inc., 329 F.3d 823 (Fed. Cir. 2003), found that a trial court that hears many patent cases, the Northern District of California, committed several errors construing the term “caching policy identification information” in a patent covering data communication networks.

First, the trial court improperly read the preamble of the claim as a limitation, rather than merely a reference to the invention as a whole. But the Federal Circuit acknowledged there is no clear rule concerning when the preamble will properly function as a limitation: “Whether to treat a preamble as a claim limitation is determined on the facts of each case in light of the claim as a whole and the invention described in the patent.”

Second, making a common mistake, the district court relied on the specification and the prosecution history to read an additional limitation into the claims. But these materials are appropriately used to construe, rather than limit, the language of the claims. As the Federal Circuit conceded, “there is sometimes a fine line between reading a claim in light of the written description and relevant prosecution history, and reading a new limitation into the claim.” It found that the trial court had erroneously relied on an “inaccurate” statement in the prosecution history to limit the claims ' noting that an “inaccurate statement cannot override the claim language itself, which controls the bounds of the claim.” But, when is the prosecution history “inaccurate,” and when does it actually help the court to understand the meaning of the claims?

Third, the district court improperly used “extrinsic evidence” ' evidence outside the “intrinsic evidence” of the patent text and prosecution history ' to construe the claims. Extrinsic evidence is “appropriate only when an ambiguity remains after consulting the intrinsic evidence of record.” Again, however, it is not always easy to decide when the technical language of a patent is “ambiguous” enough to allow use of extrinsic evidence. Indeed, extrinsic evidence typically must be used to understand the meaning of technical terms of art used in the claims.

And these are far from the only ambiguous rules of claim construction. Consider the canon that “claim language generally carries the ordinary meaning of the words in their normal usage in the field of invention.” As the Federal Circuit recently said, “while this 'ordinary meaning' rule is usually expressed as a pat formula, the context supplied by the field of invention, the prior art, and the understanding of skilled artisans generally is key to discerning the normal usage of words in any claim.” Invitrogen Corp. v. Biocrest Mfg., L.P., 327 F3d 1364, 1367 (Fed. Cir. 2003). Clearly, there is ample room for debate about the “ordinary meaning” of a term in this context.

Is there a way to reverse the high reversal rate of claim construction rulings, without imposing a set of rules so rigid and desiccated that they do violence to the “true” meaning of patent claims? Unless the Federal Circuit decides to change the de novo review standard of Cybor and give deference to district court claim construction, it is hard to see how.

This article originally appeared in the New York Law Journal, an American Lawyer Media publication.