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Patent claims define the boundaries of the property right granted to inventors. But these claims, like the words with which they are written, are inherently imprecise. Recognizing this imprecision, courts have long given patent owners some penumbra of protection beyond the literal scope of their claims, under what is known as the doctrine of equivalents. In Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., No. 00-1543, 2002 U.S. Lexis 3818 (May 28, 2002), the U.S. Supreme Court vacated the prior decision of the U.S. Court of Appeals for the Federal Circuit, rejecting that court’s per se rule of the doctrine’s inapplicability and holding that the doctrine must be applied in a more flexible manner. There has long been a tension in patent law between applying the doctrine of equivalents to ensure a patent owner an adequate measure of protection and enabling a patent to perform a notice function by allowing competitors of the patent owner to determine what does and does not infringe. To reduce the level of uncertainty, several rules have been developed which define situations in which the doctrine may not be applied as a matter of law. One of the most important of these is “prosecution history estoppel,” which states that a patent owner may not recapture through the doctrine any subject matter surrendered while negotiating the claim with the U.S. Patent and Trademark Office (PTO) during the patent application process. See, e.g., Loctite Corp. v. Ultraseal Ltd., 781 F.2d 861, 870 (Fed. Cir. 1985). In its most common flavor, prosecution history estoppel arises when a patent applicant amends a claim to overcome a rejection made by the PTO, such as, for example, narrowing the scope of the claim to distinguish the invention from the prior art. THE FEDERAL CIRCUIT’S ABSOLUTE BAR APPROACH In an effort to resolve the tension in favor of the notice function of patents, the Federal Circuit in Festocreated what it called an “absolute bar,” under which any narrowing amendment made to a claim element completely barred the application of the doctrine of equivalents as to that element. 234 F.3d 558, 569 (Fed. Cir. 2000). The absolute bar approach was a radical departure from the established approach, which allowed some room for equivalents by focusing on the specific subject matter surrendered, and many viewed it as opening a Pandora’s box of potential problems for patent litigators, prosecutors and counselors alike. In Festo, the Supreme Court found the absolute bar to be too much of a concession to certainty and efficiency at the expense of legitimate expectations in a property right, and overturned it in favor of a “flexible bar” approach that allows some scope of equivalents even for claim elements that have been amended. Festoarose from the alleged infringement by SMC of Festo’s two patents for a magnetic rodless cylinder that uses magnets to move objects in a conveying system. During prosecution, Festo added narrowing limitations to the claims in response to a rejection under 35 U.S.C. 112, which deals with requirements relating to the form of the claims. SMC’s device was found not literally to infringe Festo’s narrowed claims, but Festo alleged that it infringed under the doctrine of equivalents. SMC argued that Festo should be barred from asserting the doctrine with respect to these elements because they had been added during prosecution in order to obtain the patents. The district court held that the amendments did not give rise to estoppel, and the Federal Circuit, sitting en banc, reversed. A unanimous Supreme Court opinion, authored by Justice Anthony M. Kennedy, addressed two questions in Festo. The first was whether an amendment made for reasons other than to overcome a prior art rejection, such as to overcome the � 112 rejection at issue, may give rise to a prosecution history estoppel. As was expected, the Court answered yes, agreeing with the Federal Circuit. The second question — the appropriateness of the absolute bar — was more controversial, and its answer was awaited with much more anticipation. On this issue, the Supreme Court vacated the Federal Circuit’s decision and held that while making a narrowing amendment to a claim element creates a presumption that the doctrine of equivalents cannot be applied, this presumption can be rebutted with a showing that the equivalent at issue was not in fact surrendered. The Supreme Court began with a discussion of the rationale for the doctrine of equivalents, which it described in terms of a balance between meaningful protection of the inventor’s property right and the need for certainty in determining the scope of the patent monopoly. The Court plainly recognized the need for the doctrine, stating that “the nature of language makes it impossible to capture the essence of a thing in a patent application.” While recognizing that the doctrine renders the scope of patents less certain, the Court stated that “this uncertainty is the price for ensuring appropriate incentives for innovation.” 2002 U.S. Lexis, at *17, *19. On the other hand, the Court explained that prosecution history estoppel is necessitated by the need to prevent the patentee from effectively circumventing the role of the PTO as a gatekeeper, by giving up claim scope to achieve issuance of a patent during prosecution and then asserting infringement based upon the relinquished subject matter under the guise of the doctrine. The Court agreed with the Federal Circuit that prosecution history estoppel may arise from any narrowing amendment made to satisfy the statutory requirements for a patent, including an amendment made in response to a rejection under � 112. The Court reasoned that by making a narrowing amendment, the patentee has disclaimed the subject matter at issue, regardless of whether the need to do so arose due to prior art or an insufficiency in the form of the claims. The Supreme Court condemned the complete-bar approach as disruptive of long-settled law and the expectations of existing patentees, and as inconsistent with the purpose of prosecution history estoppel. That is, estoppel presumes that a narrowing amendment is a concession that the scope of the patent does not extend as far as the original claim. “It does not follow, however, that the amended claim becomes so perfect in its description that no one could devise an equivalent.” Id. at *29. The Court further noted the fundamental unfairness of an absolute bar rule to inventors who amended their claims under the old regime and had no reason to think that they would be surrendering all equivalents. The Supreme Court’s flexible bar gives a patent owner some room to argue that a claim element which has been narrowed is entitled to a range of equivalence. But the patent owner has a tougher task now than under the law as it existed before the Federal Circuit’s decision in Festo: The new flexible bar carries with it a presumption that the amendment did in fact surrender the particular equivalent in question. The high court stated that the presumption may be rebutted by the patentee’s showing that “at the time of amendment one skilled in the art could not reasonably be expected to have drafted a claim that would have literally encompassed the alleged equivalent.” Id. at *34. The Court offered three more specific instances in which this presumption might be overcome: when the equivalent was unforeseeable at the time of application, when the rationale for the amendment bears no more than a tangential relation to the equivalent or when there is some other reason suggesting that the patentee could not reasonably be expected to have described the equivalent. The new flexible bar is certainly not as draconian to the patent owner as the complete bar rule, and the Court went out of its way to say that it is not just “the complete bar by another name.” But the patentee still faces higher hurdles than existed before Festo. When a claim element has been amended and infringement depends upon establishing that the accused product includes an equivalent to that element, the patentee must explain why an application of the doctrine of equivalents should not be barred. THE IMPORTANCE OF BEING UNFORESEEABLE The Court’s discussion of unforeseeability is an extremely important component of this decision, and it is likely that arguing that an accused equivalent was unforeseeable will become the cleanest and most common way that a presumption of prosecution history estoppel will be rebutted. But beyond that, the Federal Circuit, or at least some of its judges, may well extend the Supreme Court’s opinion to establish a new limitation to the doctrine, which would bar applying the doctrine to cover equivalents that were foreseeable, even outside the context of prosecution history estoppel. The high court’s statement that “[t]he patentee, as the author of the claim language, may be expected to draft claims encompassing readily known equivalents” ( id. at *33) will likely be seized upon by the Federal Circuit to support this. The development of such a foreseeability limitation would not be at all inconsistent with observable trends in other Federal Circuit decisions. For example, in its most recent en banc decision, Johnson & Johnston Assoc. Inc. v. R.E. Service Co. Inc., 285 F.3d 1046, 1054 (Fed. Cir. 2002), the Federal Circuit held that subject matter disclosed but not claimed in the patent — perhaps the ultimate example of subject matter that is foreseeable — is dedicated to the public, and may not be recaptured through the doctrine of equivalents. The foreseeability of an accused equivalent, which is becoming an increasingly important factor in Federal Circuit infringement analysis, will likely become even more so in the wake of the Festodecision. Michael P. Sandonato, [email protected], is a partner at New York’s Fitzpatrick, Cella, Harper & Scinto, www.fchs.com, and is active in all aspects of the firm’s patent practice, including litigation, licensing and transactions, patent prosecution and client counseling. Carl B. Wischhusen, [email protected], is an associate at the firm and specializes in patent prosecution and the preparation of patent applications.

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