The case of Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd. presented the Supreme Court with the opportunity to clarify the relationship between the doctrine of equivalents and prosecution history estoppel. This case was significant in determining how amendments made during patent prosecution impact a patentee’s ability to claim infringement under the doctrine of equivalents. The Court examined whether prosecution history estoppel applied only to amendments made to overcome prior art or whether it extended to amendments made for any reason related to patentability. Furthermore, the Court addressed whether estoppel completely barred all equivalents or whether some equivalents could still be claimed.

Factual Background:

• Festo Corporation owned two patents related to an industrial device, a rodless cylinder used for various applications such as sewing machinery and amusement park rides.
• During the patent prosecution process, the claims were amended to add limitations, including the use of a pair of one-way sealing rings and a magnetizable sleeve.
• After Festo introduced its patented device to the market, Shoketsu Kinzoku Kogyo Kabushiki Co. (SMC) released a similar device that featured a single two-way sealing ring and a non-magnetizable sleeve.
• Festo sued SMC for patent infringement under the doctrine of equivalents, arguing that the accused device performed substantially the same function in substantially the same way to achieve substantially the same result.

Procedural Background:

• The District Court ruled in favor of Festo, rejecting SMC’s argument that prosecution history estoppel barred Festo from asserting infringement under the doctrine of equivalents.
• Initially, the Federal Circuit affirmed this decision.
• However, the Supreme Court vacated and remanded the case in light of its decision in Warner-Jenkinson Co. v. Hilton Davis Chemical Co., which reaffirmed the applicability of prosecution history estoppel.
• On remand, the en banc Federal Circuit reversed its earlier ruling, holding that prosecution history estoppel applied and adopting a complete bar, preventing any claim of equivalence for the amended claim elements.
• The Supreme Court then granted certiorari to resolve this issue.

Issues Involved:

• Whether prosecution history estoppel applies only to amendments made to avoid prior art or to all amendments made for reasons related to patentability.
• Whether prosecution history estoppel constitutes a complete bar, precluding all claims of equivalence, or whether certain equivalents may still be asserted.

Submissions of the Parties:

Petitioner (Festo Corporation):

• Argued that prosecution history estoppel should only apply to amendments made to avoid prior art and not to amendments made for other patentability-related reasons, such as compliance with 35 U.S.C. § 112.
• Contended that the Federal Circuit's complete-bar approach was inconsistent with prior precedent and unduly restricted the scope of patent protection.
• Asserted that patentees should retain some flexibility to claim equivalents unless they clearly surrendered those equivalents during prosecution.

Respondent (SMC):

• Argued that any narrowing amendment made during patent prosecution constituted a surrender of subject matter and that prosecution history estoppel should apply broadly.
• Supported the Federal Circuit’s complete-bar rule, asserting that it provided clarity and reduced uncertainty in infringement litigation.
• Contended that permitting any claim of equivalence after an amendment undermines the notice function of patents.

Discussion on Cited Judgments:

• Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997) – Reaffirmed the doctrine of equivalents but also emphasized that prosecution history estoppel serves as a check against expanding patent claims beyond what was surrendered during prosecution.
• Exhibit Supply Co. v. Ace Patents Corp., 315 U.S. 126 (1942) – Established that a patentee cannot reclaim through litigation what was explicitly given up during patent prosecution.
• Goodyear Dental Vulcanite Co. v. Davis, 102 U.S. 222 (1880) – Held that amendments made to secure a patent limit the scope of what can be claimed later as an equivalent.
• Graver Tank & Mfg. Co. v. Linde Air Products Co., 339 U.S. 605 (1950) – Reaffirmed that the doctrine of equivalents protects patentees from insubstantial variations that avoid literal infringement.

Reasoning and Analysis:

• The Supreme Court ruled that prosecution history estoppel applies to any narrowing amendment made to comply with the requirements of the Patent Act, not just those made to avoid prior art.
• The Court reasoned that any such amendment is a concession that the originally claimed scope was too broad.
• However, the Court rejected the Federal Circuit’s complete-bar approach, holding instead that estoppel does not automatically preclude all equivalents.
• The Court established a rebuttable presumption: when a patentee narrows a claim, it is presumed that the patentee has surrendered all equivalents. However, the patentee may rebut this presumption by demonstrating one of the following:
  • The equivalent was unforeseeable at the time of amendment.
  • The rationale for the amendment bears only a tangential relation to the equivalent.
  • Other reasons suggest that the patentee could not reasonably have described the equivalent in the original claim.
• This flexible approach ensures that patentees are held accountable for their amendments while allowing them a limited opportunity to claim equivalents in appropriate cases.

Final Decision:

• The Supreme Court vacated the Federal Circuit’s judgment and remanded the case for further proceedings to determine whether Festo could rebut the presumption of estoppel with respect to the specific equivalents in question.

Law Settled in This Case:

• Prosecution history estoppel applies to all narrowing amendments made to satisfy the requirements of the Patent Act, not just those made to avoid prior art.
• Prosecution history estoppel does not impose a complete bar on all equivalents but creates a rebuttable presumption against the patentee.
• The patentee may overcome this presumption by proving that the surrendered subject matter should still be considered an equivalent due to unforeseeability, tangential relation, or other factors.
• The ruling provides greater predictability in patent infringement cases while preserving some flexibility for patentees.

Case Title: Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd., et al.
Date of Order: May 28, 2002
Case No.: 00–1543
Neutral Citation: 535 U.S. 722 (2002)
Name of Court: Supreme Court of the United States
Name of Judge: Justice Anthony Kennedy (delivering the unanimous opinion of the Court)

Disclaimer: The information shared here is intended to serve the public interest by offering insights and perspectives. However, readers are advised to exercise their own discretion when interpreting and applying this information. The content herein is subjective and may contain errors in perception, interpretation, and presentation.

Written By: Advocate Ajay Amitabh Suman, IP Adjutor - Patent and Trademark Attorney
Email: ajayamitabhsuman@gmail.com, Ph no: 9990389539