Foreseeability as a Bar to Proof of Patent Infringement

The Court explained interchangeability in Hilton Davis Chem. Co. v. Warner-Jenkinson Co. (1997). According to the opinion, “A skilled practitioner's knowledge of interchangeability between the claimed and accused elements is not relevant for its own sake, but for what it tells the fact-finder about the similarities or differences between those elements.”

Prosecution history estoppel is a judicial gate-keeping rule decided by courts as a matter of law. The rule precludes a patentee from regaining in litigation, through assertion of equivalency, coverage of subject matter relinquished by a narrowing limitation of a claim element during prosecution of the application for the patent. The rule limits what, if anything, juries can hear about equivalents as a means of proving infringement.

In Festo, which involved the patent on a magnetically coupled rodless cylinder, the issues were as follows: Would estoppel arise after amendments were made to the patent application to narrow the claim on an element for reasons other than prior art concerns, and would this narrowing amendment absolutely restrict that element to its strict literal terms, meaning no equivalency could be asserted?

The Supreme Court held that a narrowing amendment to a patent claim during prosecution of a patent application made for any reason related to patentability ' not just to distinguish it from prior art ' can create prosecution history estoppel, but that the estoppel does not absolutely bar all equivalents for the narrowed limitation.

The Court explained that a rebuttable presumption exists, that, by narrowing a claim, a patentee has disclaimed “the territory between the original claim and the amended claim.” So, in litigation to enforce the patent, if a particular asserted infringing equivalent should fall outside the literal limits of the narrowed claim and within this surrendered territory, the patentee can overcome the presumption of disclaimer by proving that the language used in the narrowing amendment “cannot reasonably be viewed as surrendering a particular equivalent,” the Festo court wrote.

The Court gave, as examples of when this burden could be met, that the asserted equivalent (1) was unforeseeable at the time of the application; (2) is an aspect of the invention having only a peripheral or tangential relation to the reason for the narrowing amendment; or (3) for another reason could not reasonably be expected to have been described by the language of the narrowing amendment.

Fundamentally, said the Court, “[t]he patentee must show that at the time of the amendment one skilled in the art could not reasonably be expected to have drafted a claim that would have literally encompassed the alleged equivalent.”

With this rationale, the Court introduced the element of foreseeability into the exclusionary prosecution history rule to test whether claims narrowed by amendment should be absolutely restricted to their literal terms. The Festo decision does not rule on foreseeability as affecting the availability of the doctrine of equivalents for claim limitations not amended or amended in a manner that does not narrow their scope.

The foreseeability test seems to have come from an amicus brief filed in 2001 by the Institute of Electrical and Electronics Engineers-USA, which urged that, notwithstanding a patentability-based limiting amendment to a patent's claim during prosecution, the doctrine of equivalents should be permitted to apply unless the limiting effect of the amended language with respect to an accused device would have been foreseeable at the time of the amendment. This suggestion rested on the rationale in the U.S. Court of Appeals for the Federal Circuit's 1997 decision in Sage Products Inc. v. Devon Industries Inc., authored by Judge Randall R. Rader.

Sage Products did not involve prosecution history estoppel but instead turned on application of the “all-limitations rule” to specific structural limitations of a claim not narrowed by amendment during prosecution. The all-limitations rule requires equivalence for each limitation of the claim not literally infringed, not equivalence overall. According to the opinion, the claim alleged infringed required constrictions “over” and “beneath” a slot “at the top” of a container, and the accused container had two constrictions only below an opening in the top of a container. The court held that the claim location of one constriction “over” the slot must be observed under the all-limitations rule and in dicta said that: “[T]he claim at issue defines a relatively simple structural device. A skilled patent drafter would foresee the limiting potential of the “over said slot” limitation. No subtlety of language or complexity of the technology, nor any subsequent change in the state of the art, such as later-developed technology, obfuscated the significance of the limitation at the time of its incorporation into the claim. . . . [A]s between the patentee who had a clear opportunity to negotiate broader claims but did not do so, and the public at large, it is the patentee who must bear the costs of its failure to seek protection for this foreseeable alteration of its claimed structure.”

Shortly before Festo, Rader proposed that a foreseeability test be adopted for all claims, not just those narrowed by amendment in prosecution. He made this proposal in a concurring opinion in a March 2002 decision handed down by the Federal Circuit. In Johnson and Johnson Assoc. Inc. v. R.E. Service Co. Inc., the court held that a variant described in the patent application but not included in an unnarrowed claim was not subject to recapture as an equivalent. Rader concurred and proposed that the principle should be that “[t]he doctrine of equivalents does not capture subject matter that the patent drafter reasonably could have foreseen during the application process and included in the claims.”

The foreseeability test proposed by Rader for unamended or amended unnarrowed claims differs substantially in context from the proof required in Festo to overcome the prosecution history estoppel presumption arising from an amended narrowed claim. Where a patentee amends and narrows a claim during prosecution of a patent, the Supreme Court pointed out in Festo that the patentee “cannot assert that he lacked words to describe the subject matter in question. . . .[A] prior application describing the precise elements in question undercuts that premise. In that instance, the prosecution history has established that the inventor turned his attention to the subject matter in question, knew the words for both the broader and narrower claim, and affirmatively chose the latter.” In the case of an original unamended claim, however, the “prior application” is not necessarily known to the patentee.

Save for the exceptions listed in Sage Products ' principally technology developed after the patent application was in process ' Rader's foreseeability test whispers the demise of the doctrine of equivalents the Supreme Court has long defended. The premise of the foreseeability test and the premise of the doctrine of equivalents are fundamentally incompatible.

The doctrine declares as infringing accused elements that are insubstantially different from a claim limitation that does not literally describe the accused element. But if the difference is truly insubstantial, is it not a readily known equivalent, reasonably foreseeable, that could have been literally claimed?

The Supreme Court has long recognized that to prove an insubstantial difference, a patentee has been able to show that at the time of infringement one of skill in the art knew that the asserted equivalent was interchangeable with the claim element. But by showing interchangeability, does not the patentee inevitably prove that at the time of infringement the asserted equivalent was foreseeable?

Judge Alan D. Lourie, who concurred separately in Johnson and Johnston, further noted that Rader's foreseeability rule is “counterintuitive.” The alleged infringer, who to avoid equivalence normally would attempt to prove his element accused of being an equivalent is substantially different from the claimed element, instead would need to prove, for purposes of invoking the foreseeability bar, that the accused element is not substantially different and thus was foreseeable.

On the other hand, the patentee, who to prove equivalence normally would seek to prove the asserted equivalent is insubstantially different, instead would need to prove that the accused element is substantially different and therefore was not foreseeably includable within his claims. Thus, incongruously, the accused infringer is faced with admitting equivalence to invoke the foreseeability bar, and the accusing patentee is faced with denying equivalence to beat the bar. Good law cannot be this irrational.

Further, what standard prevents application of hindsight in litigation to find foreseeability, given knowledge of the accused element?

It would seem that what is insubstantially different normally would be only an obvious difference.

To guard against hindsight when deciding whether a claimed combination of elements in a patent application is obvious and unpatentable, long-standing patent law has set up the standard that there must be some suggestion or motivation in the prior art or in the knowledge generally available to one skilled in the art to make the combination of elements. But this standard seems to offer no safeguard against hindsight in application of the proposed foreseeability test. Avoidance of the patentee's claim is ample motive or suggestion for the copyist to make unimportant and insubstantial substitutes for certain claim limitations to defeat the patent.

The underlying rationale of the Supreme Court's adoption of the foreseeability rule for prosecution history estoppel is that the patentee had particular prior art before him suggesting “the words” when crafting the claim text to distinguish the prior art. In the case of an unamended claim or a not narrowingly amended claim, the appropriate words may escape the competent but not omniscient draftsman. The Supreme Court emphasized in Festo that the doctrine of equivalents exists because the nature of language makes it impossible for an inventor to capture the essence or every nuance of an invention in a patent application or to claim the invention with complete precision for the range of its novelty.

The all-limitations rule adequately polices access to the doctrine for claims not subject to the rule of prosecution history estoppel, as it did in Sage Products, and the all-limitations rule is not inconsistent with the premise of the doctrine. The foreseeability test proposed by Rader as applicable to unamended or not narrowly amended claims would make every patent infringement suit involving nonliteral infringement a contest between experts testifying on what was and was not foreseeable when the patent application was pending, testimony inevitably tainted by hindsight, and should not become law.

Solo practitioner Tim L. Burgess is a registered patent attorney in Houston. This article originally appeared in the Texas Lawyer.

The doctrine of equivalents is a rule of equity adopted more than 150 years ago by the U.S. Supreme Court. Prosecution history estoppel is a rule of equity that controls access to the doctrine. In May 2002, the Court was called upon to revisit the doctrine and the estoppel rule in Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co. Ltd. Ultimately the Court reaffirmed the doctrine and expanded the estoppel rule, but not without inciting heated debate over the Court's rationale ' especially since it included a new and controversial foreseeability test in its analysis for estoppel.

Under the doctrine, where an element of a product or process accused of patent infringement is not literally described by the express terms of a patent claim limitation, the element nevertheless may be found to infringe if there is equivalence between the element of the accused product or process and the claim limitation of the patented invention.

There is equivalence if the allegedly infringing element of the accused product performs substantially the same function in substantially the same way to obtain substantially the same result. That is, there is equivalence if the not- literally-infringing element is only insubstantially different from the original element.

The Court explained interchangeability in Hilton Davis Chem. Co. v. Warner-Jenkinson Co. (1997). According to the opinion, “A skilled practitioner's knowledge of interchangeability between the claimed and accused elements is not relevant for its own sake, but for what it tells the fact-finder about the similarities or differences between those elements.”

Prosecution history estoppel is a judicial gate-keeping rule decided by courts as a matter of law. The rule precludes a patentee from regaining in litigation, through assertion of equivalency, coverage of subject matter relinquished by a narrowing limitation of a claim element during prosecution of the application for the patent. The rule limits what, if anything, juries can hear about equivalents as a means of proving infringement.

In Festo, which involved the patent on a magnetically coupled rodless cylinder, the issues were as follows: Would estoppel arise after amendments were made to the patent application to narrow the claim on an element for reasons other than prior art concerns, and would this narrowing amendment absolutely restrict that element to its strict literal terms, meaning no equivalency could be asserted?

The Supreme Court held that a narrowing amendment to a patent claim during prosecution of a patent application made for any reason related to patentability ' not just to distinguish it from prior art ' can create prosecution history estoppel, but that the estoppel does not absolutely bar all equivalents for the narrowed limitation.

The Court explained that a rebuttable presumption exists, that, by narrowing a claim, a patentee has disclaimed “the territory between the original claim and the amended claim.” So, in litigation to enforce the patent, if a particular asserted infringing equivalent should fall outside the literal limits of the narrowed claim and within this surrendered territory, the patentee can overcome the presumption of disclaimer by proving that the language used in the narrowing amendment “cannot reasonably be viewed as surrendering a particular equivalent,” the Festo court wrote.

The Court gave, as examples of when this burden could be met, that the asserted equivalent (1) was unforeseeable at the time of the application; (2) is an aspect of the invention having only a peripheral or tangential relation to the reason for the narrowing amendment; or (3) for another reason could not reasonably be expected to have been described by the language of the narrowing amendment.

Fundamentally, said the Court, “[t]he patentee must show that at the time of the amendment one skilled in the art could not reasonably be expected to have drafted a claim that would have literally encompassed the alleged equivalent.”

With this rationale, the Court introduced the element of foreseeability into the exclusionary prosecution history rule to test whether claims narrowed by amendment should be absolutely restricted to their literal terms. The Festo decision does not rule on foreseeability as affecting the availability of the doctrine of equivalents for claim limitations not amended or amended in a manner that does not narrow their scope.

The foreseeability test seems to have come from an amicus brief filed in 2001 by the Institute of Electrical and Electronics Engineers-USA, which urged that, notwithstanding a patentability-based limiting amendment to a patent's claim during prosecution, the doctrine of equivalents should be permitted to apply unless the limiting effect of the amended language with respect to an accused device would have been foreseeable at the time of the amendment. This suggestion rested on the rationale in the U.S. Court of Appeals for the Federal Circuit's 1997 decision in Sage Products Inc. v. Devon Industries Inc., authored by Judge Randall R. Rader.

Sage Products did not involve prosecution history estoppel but instead turned on application of the “all-limitations rule” to specific structural limitations of a claim not narrowed by amendment during prosecution. The all-limitations rule requires equivalence for each limitation of the claim not literally infringed, not equivalence overall. According to the opinion, the claim alleged infringed required constrictions “over” and “beneath” a slot “at the top” of a container, and the accused container had two constrictions only below an opening in the top of a container. The court held that the claim location of one constriction “over” the slot must be observed under the all-limitations rule and in dicta said that: “[T]he claim at issue defines a relatively simple structural device. A skilled patent drafter would foresee the limiting potential of the “over said slot” limitation. No subtlety of language or complexity of the technology, nor any subsequent change in the state of the art, such as later-developed technology, obfuscated the significance of the limitation at the time of its incorporation into the claim. . . . [A]s between the patentee who had a clear opportunity to negotiate broader claims but did not do so, and the public at large, it is the patentee who must bear the costs of its failure to seek protection for this foreseeable alteration of its claimed structure.”

Shortly before Festo, Rader proposed that a foreseeability test be adopted for all claims, not just those narrowed by amendment in prosecution. He made this proposal in a concurring opinion in a March 2002 decision handed down by the Federal Circuit. In Johnson and Johnson Assoc. Inc. v. R.E. Service Co. Inc., the court held that a variant described in the patent application but not included in an unnarrowed claim was not subject to recapture as an equivalent. Rader concurred and proposed that the principle should be that “[t]he doctrine of equivalents does not capture subject matter that the patent drafter reasonably could have foreseen during the application process and included in the claims.”

The foreseeability test proposed by Rader for unamended or amended unnarrowed claims differs substantially in context from the proof required in Festo to overcome the prosecution history estoppel presumption arising from an amended narrowed claim. Where a patentee amends and narrows a claim during prosecution of a patent, the Supreme Court pointed out in Festo that the patentee “cannot assert that he lacked words to describe the subject matter in question. . . .[A] prior application describing the precise elements in question undercuts that premise. In that instance, the prosecution history has established that the inventor turned his attention to the subject matter in question, knew the words for both the broader and narrower claim, and affirmatively chose the latter.” In the case of an original unamended claim, however, the “prior application” is not necessarily known to the patentee.

Save for the exceptions listed in Sage Products ' principally technology developed after the patent application was in process ' Rader's foreseeability test whispers the demise of the doctrine of equivalents the Supreme Court has long defended. The premise of the foreseeability test and the premise of the doctrine of equivalents are fundamentally incompatible.

The doctrine declares as infringing accused elements that are insubstantially different from a claim limitation that does not literally describe the accused element. But if the difference is truly insubstantial, is it not a readily known equivalent, reasonably foreseeable, that could have been literally claimed?

The Supreme Court has long recognized that to prove an insubstantial difference, a patentee has been able to show that at the time of infringement one of skill in the art knew that the asserted equivalent was interchangeable with the claim element. But by showing interchangeability, does not the patentee inevitably prove that at the time of infringement the asserted equivalent was foreseeable?

Judge Alan D. Lourie, who concurred separately in Johnson and Johnston, further noted that Rader's foreseeability rule is “counterintuitive.” The alleged infringer, who to avoid equivalence normally would attempt to prove his element accused of being an equivalent is substantially different from the claimed element, instead would need to prove, for purposes of invoking the foreseeability bar, that the accused element is not substantially different and thus was foreseeable.

On the other hand, the patentee, who to prove equivalence normally would seek to prove the asserted equivalent is insubstantially different, instead would need to prove that the accused element is substantially different and therefore was not foreseeably includable within his claims. Thus, incongruously, the accused infringer is faced with admitting equivalence to invoke the foreseeability bar, and the accusing patentee is faced with denying equivalence to beat the bar. Good law cannot be this irrational.

Further, what standard prevents application of hindsight in litigation to find foreseeability, given knowledge of the accused element?

It would seem that what is insubstantially different normally would be only an obvious difference.

To guard against hindsight when deciding whether a claimed combination of elements in a patent application is obvious and unpatentable, long-standing patent law has set up the standard that there must be some suggestion or motivation in the prior art or in the knowledge generally available to one skilled in the art to make the combination of elements. But this standard seems to offer no safeguard against hindsight in application of the proposed foreseeability test. Avoidance of the patentee's claim is ample motive or suggestion for the copyist to make unimportant and insubstantial substitutes for certain claim limitations to defeat the patent.

The underlying rationale of the Supreme Court's adoption of the foreseeability rule for prosecution history estoppel is that the patentee had particular prior art before him suggesting “the words” when crafting the claim text to distinguish the prior art. In the case of an unamended claim or a not narrowingly amended claim, the appropriate words may escape the competent but not omniscient draftsman. The Supreme Court emphasized in Festo that the doctrine of equivalents exists because the nature of language makes it impossible for an inventor to capture the essence or every nuance of an invention in a patent application or to claim the invention with complete precision for the range of its novelty.

The all-limitations rule adequately polices access to the doctrine for claims not subject to the rule of prosecution history estoppel, as it did in Sage Products, and the all-limitations rule is not inconsistent with the premise of the doctrine. The foreseeability test proposed by Rader as applicable to unamended or not narrowly amended claims would make every patent infringement suit involving nonliteral infringement a contest between experts testifying on what was and was not foreseeable when the patent application was pending, testimony inevitably tainted by hindsight, and should not become law.

Solo practitioner Tim L. Burgess is a registered patent attorney in Houston. This article originally appeared in the Texas Lawyer.