Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd.
535 U.S. 722 (2002)
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Rule of Law:
A narrowing amendment to a patent claim made for a reason related to patentability does not create a complete bar against the doctrine of equivalents. Instead, it creates a rebuttable presumption that the patentee has surrendered the subject matter between the original and the amended claims, which the patentee may overcome by showing the alleged equivalent was unforeseeable at the time of the amendment.
Facts:
- Festo Corporation owned two patents for a magnetic rodless cylinder, a piston-driven device used in conveying systems.
- During the patent application process, Festo amended its applications in response to an examiner's objections regarding clarity and form under 35 U.S.C. § 112.
- One amendment added a new limitation requiring the invention to contain a pair of one-way sealing rings.
- Another amendment added the limitation that the device's outer shell, or sleeve, must be made of a magnetizable material.
- After Festo's patents were issued, Shoketsu Kinzoku Kogyo Kabushiki Co. (SMC) began marketing a similar device.
- SMC's device used a single sealing ring with a two-way lip, instead of two one-way rings.
- SMC's device also used a nonmagnetizable alloy for its sleeve.
- Due to these differences, SMC's device did not literally infringe the claims in Festo's patents.
Procedural Posture:
- Festo Corporation sued SMC in the U.S. District Court for the District of Massachusetts for patent infringement under the doctrine of equivalents.
- The District Court found for Festo, holding that its amendments did not create estoppel.
- On appeal by SMC, a panel of the Court of Appeals for the Federal Circuit affirmed the district court's decision.
- The U.S. Supreme Court granted certiorari, vacated the judgment, and remanded for reconsideration in light of an intervening decision.
- On remand, the Court of Appeals for the Federal Circuit, sitting en banc, reversed the District Court, holding that any narrowing amendment creates a 'complete bar' to the doctrine of equivalents for the amended element.
- Festo Corporation (petitioner) was granted a writ of certiorari by the U.S. Supreme Court to review the Federal Circuit's 'complete bar' rule.
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Issue:
Does a narrowing amendment to a patent claim, made for a reason related to patentability, create a complete bar that prevents the patent holder from asserting infringement against any equivalent to the amended element under the doctrine of equivalents?
Opinions:
Majority - Justice Kennedy
No. A narrowing amendment to a patent claim does not act as a complete bar to the doctrine of equivalents. The Court rejected the Federal Circuit's 'complete bar' rule, finding it inconsistent with precedent and the nature of language, which cannot perfectly capture an invention. While an amendment made for any reason related to patentability gives rise to estoppel, it does not automatically surrender all possible equivalents. To do so would disrupt the settled expectations of patentees who amended claims under the prior 'flexible bar' regime. Instead, the Court established a rebuttable presumption: a narrowing amendment is presumed to surrender all subject matter between the original broader claim and the amended narrower claim. The patentee bears the burden of rebutting this presumption by showing that the alleged equivalent was unforeseeable at the time of the amendment, that the rationale for the amendment was only tangentially related to the equivalent, or that there was some other reason the patentee could not have been reasonably expected to have described the alleged equivalent.
Analysis:
This decision established a significant middle ground between the prior 'flexible bar' and the Federal Circuit's 'complete bar' for prosecution history estoppel. By creating a rebuttable presumption, the Court provided more certainty to competitors, who can generally assume that narrowed claim language represents a surrender of subject matter. However, it preserves a pathway for patentees to protect their inventions from infringement by truly unforeseeable equivalents, thus maintaining the value of the doctrine of equivalents. The ruling forces both patentees and litigators to carefully analyze the prosecution history to determine not just if an amendment was made, but also whether a specific equivalent could have been reasonably foreseen and claimed at the time.
