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Newsletters and Bulletins / August 2002 / United States (US)

United States - Doctrine of Equivalents

For the past few years a number of academic writers have been suggesting that the only legitimate purpose of the doctrine of equivalents, whereby something falling outside the literal scope of a patent claim may be found to be an infringement of that claim, is to provide the patentee with protection against others who replace one of the elements set out in the claims with something that was itself not yet invented at the time the patent in question was applied for. Otherwise, such writers opine, the patentee should be bound by the wording of his claims since, if he failed to cover known alternatives to what was set out in his claim, he had only himself to blame by writing his claim too narrowly. This view is, of course, not yet the law. However, recent decisions of the United States Supreme Court and the Court of Appeal for the Federal Circuit seem to show that at least some of the judges may have sympathy for this academic approach.

In the Supreme Court case, Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., the court considered two aspects of the decision by the Federal Circuit Court of Appeals noted in our February 2002 Newsletter. The first was whether the Federal Circuit had been correct to hold that an estoppel arose limiting the application of the doctrine of equivalents whenever claims had been narrowed for reasons relating to patentability during proceedings in the Patent Office leading up to grant of the patent. The second related to the scope of any estoppel that was created.

Before addressing these two questions, however, the court stated the purpose of the doctrine. Writing for a unanimous court, Justice Kennedy stated:

Unfortunately, the nature of language makes it impossible to capture the essence of a thing in a patent application. ... 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.

It is true that the doctrine of equivalents renders the scope of patents less certain. ... If competitors cannot be certain about a patent's extent they may be deterred from engaging in legitimate manufactures outside its limits or may invest by mistake in competing products that the patent secures. These concerns ...however, are not new. Each time the Court has considered the doctrine, it has acknowledged this uncertainty as the price for securing the appropriate incentives for innovation, and it has affirmed the doctrine over dissents that urged a more certain rule.

On the first of the questions before it in the present case, the Supreme Court agreed with the Court of Appeals for the Federal Circuit and rejected arguments that the only types of amendment that should give rise to an estoppel were those that were made to distinguish the invention over the prior art. The Court stated:

Estoppel arises when an amendment is made to secure the patent and the amendment narrows the patent's scope. If [an] .. amendment is truly cosmetic, then it would not narrow the patent's scope or raise an estoppel. On the other hand, if [an] ... amendment is necessary and narrows the patent's scope - even if only for the purpose of a better description - estoppel may apply. A patentee who narrows a claim as a condition for obtaining a patent disavows his claim to broader subject matter, whether the amendment is made to avoid the prior art or to comply with Section 112.

Section 112 is the section which, among other things, requires that a claim distinctly point out the nature of the invention (which requirement is normally understood to mean that the claim is clear and that the specification contains a written description of the invention and a disclosure enabling one skilled in the art to practice the invention commensurate with the scope of the claims).

On the second question, the Supreme Court disagreed with the Federal Circuit. The Federal Circuit's decision which was under consideration had held that, if an estoppel existed as a result of a narrowing amendment, then the element of the claim to which the estoppel applied was to be applied literally without any application of the doctrine of equivalents. The Supreme Court viewed this as being too harsh and contrary to prior case law. In its view, it was necessary that there was some flexibility in the application of the estoppel. However, the court did not endorse a total flexibility on a totality of the circumstances basis to see what it was that the patentee could be regarded as having given up by his amendment as some had hoped. The Supreme Court made the following points.

1) When the court is unable to determine the purpose underlying a narrowing amendment - and hence a rationale for limiting the surrender to particular equivalents - the court should presume that the patentee surrendered all subject matter between the broader and the narrower language.

2) The patentee should bear the burden of showing that the amendment does not surrender the particular equivalent in question.

3) The patentee, as the author of the claim language, may be expected to draft claims encompassing readily known equivalents. A patentee's decision to narrow his claims through amendment may be presumed to be a general disclaimer of the territory between the original claim and the amended claim.

4) There are some cases...where the amendment cannot reasonably be viewed as surrendering a particular equivalent. The equivalent may have been unforeseeable at the time of the application; the rationale underlying the amendment may bear no more than a tangential relation to the equivalent in question; or there may be some other reason suggesting that the patentee could not reasonably have been expected to have described the insubstantial substitute in question.

In application of the fourth of these points, the court indicated that the patentee bore the burden of showing "that at the time of the amendment one skilled in the art could not reasonably have been expected to have drafted a claim that would have literally encompassed the alleged equivalent."

The second case in which the academic writers' foreseeability issues arose was Johnson & Johnston Associates Inc. v. R.E. Service Co. The issue was whether something disclosed in the patent specification, but falling outside the claims of the patent, could be found to be an infringement of the patent under the doctrine of equivalents. The claims specified the use of aluminum sheet. The specification stated "while aluminum is currently preferred ..., other metals such as stainless steel or nickel alloys may be used." The case was heard en banc by the Federal Circuit Court of Appeals in view of the fact that there was an apparent conflict between two of its own prior decisions on this issue. In a 12-1 decision, the Court held that when a patent drafter discloses but declines to claim subject matter "...this action dedicates that unclaimed subject matter to the public. Application of the doctrine of equivalents to recapture subject matter deliberately left unclaimed would conflict with the primacy of the claims in defining the scope of the patentee's exclusive right."

The main reason for the decision was "a patentee cannot narrowly claim an invention to avoid prosecution scrutiny by the PTO, and then after the patent issuance, use the doctrine of equivalents to establish infringement because the specification discloses the equivalents."

The one dissenting judge, Judge Newman, felt that the majority opinion established new law which was contrary to a prior Supreme Court decision, the famous Graver Tank decision, in which the specification had mentioned the subject matter falling outside the claims which was found to be an infringement under the doctrine of equivalents. The majority distinguished Graver Tank on the ground that there had been no dedication of unclaimed subject matter to the public in that case. The patentee had in fact included broad claims covering the subject matter in question, but these had been found to be invalid.

Additional reasons given by the various judges for the majority opinion differed among themselves. One group, adopting the academic writers' foreseeability test, took the view that "the doctrine of equivalents does not capture subject matter that the patent drafter could reasonably have foreseen during the application process and included in the claims". If something is mentioned in the specification, it was foreseen. Judge Lourie specifically disagreed with this approach, pointing out that this would add yet another complexity to an already complex situation by requiring factual determinations as to what was or was not foreseeable. He was also troubled by the potential interaction between a foreseeability test and validity issues relating to findings of obviousness.

For the time being, therefore, the issue of foreseeability is confined to deciding on the effect of an amendment during prosecution on the application of the doctrine of equivalents; however, we probably have not heard the last of attempts to expand it to the application of the doctrine of equivalents as a whole.

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