Are We Overstating the Federal Circuit’s Festo Decision?

The Federal Circuit’s Festo decisioni has generated extensive interest within the legal community and the popular press. The overwhelming majority of commentary has bitterly complained about Festo‘s impact on the doctrine of equivalents.ii The decision has been characterized as an “emasculation” of that doctrine, and some have gone so far as to suggest that Festo is a government “taking” because of its impact on the scope of many unexpired patents. We should take care, however, not to overstate Festo

The Federal Circuit has indeed eliminated all remnants of the “flexible bar” approach to prosecution history estoppel, which approach limited the scope of the doctrine of equivalents “within a spectrum ranging from great to small to zero.”iii In response to En Banc Question 3, the Federal Circuit embraced a “complete bar,” holding that no range of equivalents is available when an element has been narrowed during prosecution for any reason related to the statutory requirements of a patent.

The complete bar approach of Festo has met a fury of criticism. It should not be overlooked, however, that Festo’s complete bar is explicitly restricted in its applicability. More significantly, the complete bar is no more than a logical extension of existing Supreme Court jurisprudence.

Festo’s Complete Bar Has Narrow Applicability 

The complete bar of Festo is restricted to those particular claim elements that were amended during prosecution. Claim elements that have not been narrowed (and of course those that have not been amended at all) are left unscathed.

We should appreciate that the vast majority of claim elements in any particular patent are unchanged during prosecution. The doctrine of equivalents fully applies to such unchanged claim elements, as before. According to Festo, “once an element of a claim is narrowed by amendment . . ., [only] that element’s scope of coverage will not extend beyond its literal terms.”iv The phrase “with respect to the amended claim element” prominently appears in the Federal Circuit’s answers to En Banc Questions 1 and 2.

The holding of Festo is also explicitly restricted to those claim amendments that narrow the scope of a claim, but this aspect of the Federal Circuit’s decision is often underappreciated or simply overlooked. Festo clearly provides that only “a narrowing amendment . . . will give rise to prosecution history estoppel.”v In fact, Festo establishes the nature of a claim amendment as a threshold question: “[T]he court first must determine whether the amendment narrowed the literal scope of the claim.”vi Only when answered affirmatively can the court find prosecution history estoppel. The complete bar of Festo therefore reaches only a subset of the claim amendments (narrowing amendments) of another subset of claim amendments (amendments related to patentability) for a small subset of claim elements (only those claim elements amended during prosecution).

Another point of contention raised by Festo is the extension of prosecution history estoppel beyond narrowing amendments made to overcome prior art. In response to En Banc Question 1, the Federal Circuit has indeed held that “a substantial reason related to patentability” includes any reason related to the statutory requirements for a patent. Narrowing claim amendments made to overcome rejections under 35 U.S.C. ? 112 will therefore trigger a complete bar under Festo. While many commentators have complained that this aspect of Festo unduly limits the doctrine of equivalents, such complaints beg the question: How often are amendments actually narrowing when made solely to overcome 35 U.S.C. ? 112 rejections?

Festo’s Complete Bar Approach is a Logical Extension of Supreme Court Jurisprudence

With respect to its adoption of a complete bar, Festo is nothing more than a logical extension of existing jurisprudence. Prosecution history estoppel has historically prevented a patentee from using the doctrine of equivalents to cover subject matter that the patentee relinquished during patent prosecution, and it is well settled that surrendered subject matter should not be recaptured.

Sheppard v. Carriganvii (1886):
If an applicant, in order to get his patent, accepts one with a narrower claim than that contained in his original application he is bound by it.
viii

Smith v. Magic City Kennel Clubix (1931):
[L]imitations imposed by the inventor, especially such as were introduced into an application after it had been persistently rejected, must be strictly construed against the inventor and looked upon as disclaimers.

[W]here a patentee has narrowed his claim, in order to escape rejection, he may not “by resort to the doctrine of equivalents, give to the claim the larger scope which it might have had without the amendments which amount to disclaimer.”x

Exhibit Supply v. Ace Patentsxi (1942):
By the amendment [the patentee] recognized and emphasized the difference between the [claim before and after its amendment] and proclaimed his abandonment of all that is embraced in that difference. . . . The difference which he thus disclaimed must be regarded as material, and since the amendment operates as a disclaimer of that difference it must be strictly construed against [the patentee].

It follows that what the patentee, by a strict construction of the claim, has disclaimed . . . cannot now be regained by recourse to the doctrine of equivalents, which at most operates, by liberal construction, to secure to the inventor the full benefits, not disclaimed, of the claims allowed.xii

Graham v. John Deerexiii (1966):
[C]laims that have been narrowed in order to obtain the issuance of a patent by distinguishing the prior art cannot be sustained to cover that which was previously by limitation eliminated from the patent.

Here, the patentee obtained his patent only by accepting the limitations imposed by the examiner. . . . The subject matter as a whole reduces, then, to the distinguishing features clearly incorporated into the claims.xiv

These decisions illustrate the Supreme Court’s continued endorsement of the principle that narrowing claim amendments amount to “disclaimers” and should be strictly construed against the patentee. And Exhibit Supply squarely addressed the difference in claim scope before and after a narrowing amendment and proclaimed that the amendment operates as a disclaimer of that difference. This is nothing less than a complete bar.

The foregoing Supreme Court decisions dealt with claim amendments clearly made to overcome prior art. In Warner-Jenkinson,xv the Supreme Court addressed the situation where the reason for a claim amendment is unclear:

Where no explanation [for a claim amendment] is established, . . . the court should presume that the PTO had a substantial reason related to patentability for including the limiting element added by amendment. In those circumstances, prosecution history estoppel would bar the application of the doctrine [of] equivalents as to that element.xvi

In Warner-Jenkinson, the Supreme Court therefore created a presumption (“the WarnerJenkinson presumption”) that a claim amendment is related to patentability when the reason for the amendment is unclear from the prosecution history. That presumption becomes conclusive if unrebutted by the patentee with evidence that the amendment was made for reasons other than patentability. Prosecution history estoppel arising from the WarnerJenkinson presumption completely bars application of the doctrine of equivalents.xvii In effect, the WarnerJenkinson presumption penalizes those patentees that leave behind an unclear record in the prosecution history as to why amendments had been made.

WarnerJenkinson did not reach the question, however, of whether a flexible bar or a complete bar should result when the reason for an amendment is clearly related to patentability. Pre-Festo Federal Circuit decisions have indicated that the flexible bar survived WarnerJenkinson.xviii Therefore, narrowing claim amendments under the pre-Festo scheme could lead to one of three possibilities:

● no bar to the doctrine of equivalents based on prosecution history estoppel where (a) it is clear from the prosecution history that the amendment was unrelated to patentability or (b) the patentee establishes that an amendment was not made for reasons of patentability (thereby overcoming the WarnerJenkinson presumption);

● a flexible bar where the amendment was clearly made for reasons of patentability; or

● a complete bar where (a) the reason for an amendment is unclear from the prosecution history and (b) it is unrebutted by the patentee that the amendment was made for reasons of patentability (thereby failing to overcome the WarnerJenkinson presumption).

Festo leaves only two possibilities: either the doctrine of equivalents is completely barred by prosecution history estoppel for every narrowing amendment related to patentability or there is no bar. Remnants of the flexible bar approach have, therefore, been eliminated by Festo’s all-or-nothing approach.

If indeed the Supreme Court agrees with the Federal Circuit’s conclusion that the flexible bar is unworkable, it would be merely a logical extension of WarnerJenkinson to impose a complete bar to the application of the doctrine of equivalents whenever prosecution history estoppel is found. The complete bar “penalty” is already firmly in place for unexplained amendments under the WarnerJenkinson presumption. And with respect to amendments clearly made for reasons of patentability, the Supreme Court has long-ago endorsed the propositions that amendments act to disclaim the difference in claim scope before and after a narrowing amendment and that disclaimed subject matter can not be recaptured by resort to the doctrine of equivalents.

We are all eagerly awaiting the final word on Festo. The Supreme Court is now charged with deciding the following issues:

Whether every claim narrowing amendment designed to comply with any requirement of the Patent Act?including those not related to prior art?automatically creates prosecution history estoppel.

Whether every finding of prosecution history estoppel completely bars every application of the doctrine of equivalents.

The first issue revisits whether narrowing amendments not related to prior art, such as amendments made in response to rejections under 35 U.S.C ? 112, should trigger prosecution history estoppel. The second issue addresses Festo’s elimination of the flexible bar.

The extension of WarnerJenkinson, in the manner proposed by the Federal Circuit’s Festo decision, would equate the penalty for disclaimers of subject matter with that for unexplained amendments. The Supreme Court may find it difficult to rationalize a scheme (such as the pre-Festo scheme) in which the penalty for unexplained amendments is more severe than that for narrowing amendments clearly made for reasons of patentability.

We should not be surprised, therefore, if the Supreme Court takes this opportunity to extend WarnerJenkinson to uphold Festo’s elimination of what remains of the troublesome flexible bar. Such a decision should be considered not an “emasculation” of the doctrine of equivalents, but instead a natural extension of existing Supreme Court jurisprudence.


  1. Festo Corp . v. Shoketsu Kinzoku Kogyo Kabushiki Co., 37 U.S.P.Q.2d 1161 (Fed. Cir. 1995), vacated & remanded for further consideration in view of Hilton Davis, 117 S. Ct. 1240 (1997), on remand, 50 U.S.P.Q.2d 1385 (Fed. Cir. 1999), reh’g in banc granted, 51 U.S.P.Q.2d 1959 (Fed. Cir. 1999), in banc decision, 234 F.3d 558, 56 U.S.P.Q.2d 1865 (Fed. Cir. 2000), cert. granted, 121 S. Ct. 2519 (U.S. June 18, 2001) (No. 00-1543).
  2. Criticisms of Festo are also of record in the amici curiae briefs filed in connection with Festo’s Petition for Writ of Certiorari and in connection with the merits of the Supreme Court review. Joan T. Kruger’s article entitled “The Views of Various Entities on the Festo Decision,” published in the Summer 2001 Issue of the Intellectual Property Law Newsletter, highlights the disparity between those organizations supporting petitioner Festo and those supporting respondent Shoketsu Kinzoku Kogyo Kabushiki.
  3. Hughes Aircraft Co. v. United States, 717 F.2d 1351, 1363, 219 U.S.P.Q. 473, 481-82 (Fed. Cir. 1983).
  4. Festo, 234 F.3d at 577, 56 U.S.P.Q.2d at 1879 (emphasis added).
  5. Id. at 566, 56 U.S.P.Q.2d at 1870 (emphasis added). That the reach of Festo is limited to narrowing amendments is stressed throughout the decision, and the phrase “amendment that narrows the scope of a claim” is prominent in the Federal Circuit’s answers to En Banc Questions 1 and 2.
  6. Id. at 586, 56 U.S.P.Q.2d at 1886 (emphasis added).
  7. Sheppard v. Carrigan, 116 U.S. 593 (1886).
  8. Id. at 598.
  9. Smith v. Magic City Kennel Club, Inc., 282 U.S. 784, 8 U.S.P.Q. 123 (1931).
  10. Id. at 790, 8 U.S.P.Q. at 125-26 (quoting Weber Electric Co. v. FreemanElectric Co., 256 U.S. 668, 677-78 (1921)).
  11. Exhibit Supply Co. v. Ace Patents Corp., 315 U.S. 126, 52 U.S.P.Q. 275 (1942).
  12. Id. at 136-37, 52 U.S.P.Q. at 279-80.
  13. Graham v. John Deere Co. of Kansas City, 383 U.S. 1, 148 U.S.P.Q. 459 (1966).
  14. Id. at 33, 148 U.S.P.Q. at 473.
  15. WarnerJenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17, 41 U.S.P.Q.2d 1865 (1997).
  16. Id. at 33, 41 U.S.P.Q.2d at 1873.
  17. The Federal Circuit confirmed that prosecution history estoppel arising from the WarnerJenkinson presumption “is total and completely ‘bars’ the application of the doctrine of equivalents as to the amended limitation.” Sextant Avionique S.A. v. Analog Devices Inc., 172 F.3d 817, 832, 49 U.S.P.Q.2d 1865, 1875 (Fed. Cir. 1999).
  18. Id. at 826, 49 U.S.P.Q.2d at 1871 (“Our case law recognizes that the scope of prosecution history estoppel ‘may have a limiting effect within a spectrum ranging from great to small to zero. The effect may or may not be fatal to application of a range of equivalents broad enough to encompass a particular accused product.'” (citing Hughes Aircraft, 717 F.2d at 1363, 219 U.S.P.Q. at 481-82)).

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