A Concise Explanation of Prosecution History Estoppel

Lock See Yu-Jahnes gives this concise explanation of prosecution history estoppel in the PLI All-Star Briefing, Vol. 5.39, on October 25, 2007:

Prosecution history estoppel is a judicially created doctrine that prevents a patentee from taking inconsistent positions regarding claim language. It requires that the claims of a patent be interpreted in light of the proceedings before the PTO during the prosecution of the application. Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki, 535 U.S. 722, 733 (2002). This means that when enforcing a patent against an alleged infringer, the patentee may not take a position regarding the interpretation of a claim that is inconsistent with actions taken before the USPTO to obtain the allowance of the claim. Amendments and comments regarding a claim limitation made during prosecution may act to limit the scope of that limitation.
Prosecution history estoppel limits the reach of the doctrine of equivalents if the claim amendment was made for a substantial reason related to patentability. Warner-Jenkinson Co., Inc. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997). In the absence of a reason for the claim amendment, there is a rebuttable presumption that the amendment was made for a substantial reason related to patentability. The Supreme Court in Festo held that an amendment made to satisfy any requirement of the Patent Act may give rise to an estoppel on infringement by equivalents. Festo, 535 U.S. at 722.

The Supreme Court also explained in Festo that there is a presumption that the patentee surrendered equivalent subject matter. This presumption may be rebutted by showing that (1) the equivalent subject matter was not foreseeable and thus not claimable at the time the application was filed, (2) the claim amendment is only tangentially related to the equivalent subject matter in dispute, or (3) the equivalent subject matter could not reasonably have been described at the time the amendment was made. Id.

The Federal Circuit interpreted Festo to hold that prosecution history estoppel applies only when a narrowing claim amendment is made for a reason substantially related to patentability. Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki, 344 F.3d 1359 (Fed. Cir. 2003). Therefore, there is a rebuttable presumption that the patentee surrendered the subject matter between the original claim and the amended claim through the narrowing amendment.

Arguments made during prosecution may give rise to estoppel. That is, claim amendments are a prerequisite for prosecution history estoppel to attach. If the arguments indicate a surrender of subject matter, then that subject matter may not be recaptured under the doctrine of equivalents during litigation.

An amendment made to a claim limitation in one claim gives rise to estoppel in an identical limitation in another claim. The scope of equivalents for the same limitation in different claims must be interpreted consistently. An argument made regarding a claim limitation will apply to the same limitation in another claim.

Rewriting a dependent claim in independent form also gives rise to prosecution history estoppel if the independent claim is canceled. Honeywell Int'l v. Hamilton Sundstrand, 370 F.3d 1131 (Fed. Cir. 2004). Likewise, a rewritten claim is considered a narrowing amendment of the independent claim.

Whether estoppel arises based on the prosecution history of a related application is determined on a case-by-case basis according to the facts. When statements made in one application are relevant to an understanding of a related application, then the patentee is bound by the statements. Microsoft v. Multi-Tech Systems, 357 F.3d 1340 (Fed. Cir. 2004). "When the applicant is seeking different claims in a divisional application, estoppel generally does not arise from the prosecution of the parent." Biogen v. Berlex Laboratories, 318 F.3d 1132 (Fed. Cir. 2003). The applicant is not barred from raising new arguments or correcting past errors.

A broadening amendment or an amendment that clarifies but does not narrow a claim limitation does not give rise to a surrender of equivalents. Business Objects v. Microstrategy, 393 F.3d 1366 (Fed. Cir. 2005). However, a narrowing amendment made voluntarily, without explanation, does not shield the amendment from a presumption that it was made for a substantial reason related to patentability. Pioneer Magnetics v. Micro Linear, 330 F.3d 1352 (Fed. Cir. 2003).

Learn more from Yu-Jahnes' "Selected Topics in Advanced Patent Prosecution" at "PLI in Brief," the online home of Practising Law Institute's weekly eNewsletter series.