Patent Equivalents and Prosecution History Estoppel--Festo

The Supreme Court Decision in Festo

In Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co.,1 the Supreme Court vacated and remanded the Federal Circuit's decision (which had established an absolute bar to equivalents where a claim had been narrowed for reasons of patentability). The Court held that a narrowing amendment made for reasons of patentability may restrict-rather than automatically absolutely bar-the scope of equivalents. Specifically, if a narrowing amendment is made during prosecution for a substantial reason related to patentability, the patentee bears the burden of rebutting the presumption that the patentee surrendered the subject matter encompassing the asserted equivalent.
As to what sort of amendment would lead to an estoppel, the Court acknowledged that the typical case involves an amendment made to avoid prior art cited against the claim, but noted that "[w]hile we made clear that estoppel applies to amendments made for a "substantial reason related to patentability," [Warner Jenkinson], at 33, we did not purport to define that term or to catalog every reason that might raise an estoppel."2 Instead of narrowing the definition of what constitutes a narrowing amendment made for a substantial reason related to patentability, the Court agreed with the Federal Circuit that a narrowing amendment made to satisfy any requirement of the statute may raise an estoppel.3 The Court went on to explicitly include amendments made to comply with 35 U.S.C. section 112:

Estoppel arises when an amendment is made to secure the patent and the amendment narrows the patent's scope. If a §112 amendment is truly cosmetic, then it would not narrow the patent's scope or raise an estoppel. On the other hand, if a §112 amendment is necessary and narrows the patent's scope-even if only for the purpose of better description-estoppel may apply. A patentee who narrows a claim as a condition for obtaining a patent disavows his claim to the broader subject matter, whether the amendment was made to avoid the prior art or to comply with §112. We must regard the patentee as having conceded an inability to claim the broader subject matter or at least as having abandoned his right to appeal a rejection. In either case estoppel may apply.4

Once it is clear that an estoppel may arise from a particular amendment, the Court rejected the absolute bar of the Federal Circuit in favor of a flexible bar:

While this Court has not weighed the merits of the complete bar against the flexible bar in its prior cases, we have consistently applied the doctrine in a flexible way, not a rigid one. We have considered what equivalents were surrendered during the prosecution of the patent, rather than imposing a complete bar that resorts to the very literalism the equivalents rule is designed to overcome. E.g., Goodyear Dental Vulcanite Co., 102 U.S., at 230; Hurlbut v. Schillinger, 130 U.S. 456, 465 (1889).5

However, relying on its prior decision in Warner-Jenkinson Co. v. Hilton Davis Chemical Co.,6 the Court placed the burden on the patentee to rebut a presumption that the amendment would trigger a complete bar as to that element or limitation:

In Warner-Jenkinson we struck the appropriate balance by placing the burden on the patentee to show that an amendment was not for purposes of patentability:
"Where no explanation is established, however, the court should presume that the patent application 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." [520 U.S.], at 33.
When the patentee is unable to explain the reason for amendment, estoppel not only applies but also "bar[s] the application of the doctrine of equivalents as to that element." Ibid. These words do not mandate a complete bar; they are limited to the circumstance where "no explanation is established." They do provide, however, that when the court is unable to determine the purpose underlying a narrowing amendment-and hence a rationale for limiting the estoppel to the surrender of particular equivalents-the court should presume that the patentee surrendered all subject matter between the broader and the narrower language.

The precise test for rebutting such a presumption is uncertain. The decision cites several types of instances where the amendment cannot reasonably be viewed as surrendering a particular element: (1) where the asserted equivalent may have been unforeseeable at the time of application; (2) where the rationale underlying the amendment bears no more than a tangential relation to the equivalent in question; or (3) where there was some other reason suggesting that the patentee could not reasonably be expected to have described the insubstantial substitute in question.7 The Court concluded that:

This presumption is not, then, just the complete bar by another name. Rather, it reflects the fact that the interpretation of the patent must begin with its literal claims, and the prosecution history is relevant to construing those claims. When the patentee has chosen to narrow a claim, courts may presume the amended text was composed with awareness of this rule and that the territory surrendered is not an equivalent of the territory claimed. In those instances, however, the patentee still might rebut the presumption that estoppel bars a claim of equivalence. The 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.8

Issues on Remand of Festo

On remand of the case from the Supreme Court,9 the Federal Circuit ordered the parties to submit additional briefing on the following issues:

We must now consider what further action to take in this case. To help us in that determination, we order the parties to submit briefs on the following issues:

1. Whether rebuttal of the presumption of surrender, including issues of foreseeability, tangentialness, or reasonable expectations of those skilled in the art, is a question of law or one of fact; and what role a jury should play in determining whether a patent owner can rebut the presumption.

2. What factors are encompassed by the criteria set forth by the Supreme Court.

3. If a rebuttal determination requires factual findings, then whether, in this case, remand to the district court is necessary to determine whether Festo can rebut the presumption that any narrowing amendment surrendered the equivalent now asserted, or whether the record as it now stands is sufficient to make those determinations.

4. If remand to the district court is not necessary, then whether Festo can rebut the presumption that any narrowing amendment surrendered the equivalent now asserted.10

NOTES

1 535 U.S. 722, 122 S. Ct. 1831, 62 USPQ2d 1705 (2002).

2. 122 S. Ct. at 1839, 62 USPQ2d at 1711.

3. 122 S. Ct. at 1839, 62 USPQ2d at 1711-12 ("We agree with the Court of Appeals that a narrowing amendment made to satisfy any requirement of the Patent Act may give rise to an estoppel.")

4 Id. at 1712.

5. Id. at 1713.

6. 520 U.S. 17 (1997).

7. Festo, 122 S. Ct. at 1842, 62 USPQ2d at 1713-14.

8. 122 S. Ct. at 1842, 62 USPQ2d at 1714.

9. Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 304 F.3d 1289, 64 USPQ2d 1698 (Fed. Cir. 2002).

10. Festo, 304 F.3d at 1290-91.