Application of Prosecution History Estoppel Confirmed

November 4, 2013

What This Means To You

  • Do not amend claims unless necessary; almost every amendment can trigger Prosecution History Estoppel.
  • If you make an amendment unrelated to patentability, state the reason for the amendment in the remarks accompanying the amendment.
  • Do not draft claims assuming the Doctrine of Equivalents will be available to you during enforcement.


In Integrated Technologies Corp. v. Rudolph Technologies, Inc., the U.S. Court of Appeals for the Federal Circuit (Federal Circuit) confirmed the basic framework of how Prosecution History Estoppel (PHE) applies, as previously laid out by the Supreme Court’s 2002 decision in Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co.

Case Background

Integrated Technology Corp. (ITC) was the owner of a patent covering inspection equipment for testing semiconductor chips. The patent’s claims related to a system for inspecting circuit card probes using a video camera by recording an image while the tip of the probe is in contact with a clear window. The issued claims require that a first image be taken while the probe tip is driven in contact with the window with a first force, and a second image be taken while the probe tip is driven in contact with the window with a second force.

ITC sued Rudolph Technologies (Rudolph) in district court for infringement under the Doctrine of Equivalents. The accused products take a first image just before contact is made with the window and a second image when the probe tip is in contact with the window. ITC argued the operation of these “no-touch” products are equivalent to the limitations of the issued claims.

As originally filed with the U.S. Patent and Trademark Office (USPTO), the claim of the patent application did not require the two images being taken while driven with two different forces. Instead, the original claim required that an image be taken with the probe tip in contact with the window. During prosecution of the patent application, however, the claim was narrowed to include the above limitations in response to a rejection based on a prior art reference. Several times during prosecution, ITC mentioned that the new limitations were not found in the prior art.

In the district court case, the jury found in favor of ITC, awarding it lost profits and finding willful infringement relating to Rudolph’s newer products. The court trebled damages for willful infringement and also awarded ITC attorneys’ fees and costs. Rudolph appealed to the Federal Circuit claiming prosecution history estoppel bars the application of the Doctrine of Equivalents.

Decision Analysis

In the decision, the Federal Circuit walked through the application of PHE as set forth in Festo. PHE prevents a patent owner from using the doctrine of equivalents to assert that an accused product infringes a patent claim when the equivalent was surrendered during prosecution in response to a rejection from the USPTO.

As set forth in Festo, PHE presumptively applies when an applicant makes a “narrowing claim amendment related to patentability” unless one of three exceptions applies: (1) the equivalent was unforeseeable at the time of the amendment; (2) the rationale for the amendment bears no more than a tangential relation to the equivalent; or (3) there is some other reason the applicant could not reasonably have been expected to describe the equivalent. The third exception was not discussed in this case.

In the present case, the Federal Circuit first addressed whether the presumption of PHE applied, answering affirmatively because it was clear that requiring two different forces be applied to the probe tip was narrower than having no such requirement.

Next, the Federal Circuit addressed whether any exceptions to PHE were present. ITC argued the amendment was not necessary to overcome the art cited by the USPTO and, therefore, the amendment was tangentially related to the equivalent. The Federal Circuit disagreed and clarified that the “tangential relation” exception was a very narrow exception and rarely used successfully. The focus of the inquiry is on “the patentee’s objectively apparent reason for the narrowing amendment.” While the amendments made by ITC may not have been necessary, ITC chose to make them in response to a rejection. Moreover, ITC repeatedly made statements during prosecution that the added limitations were what made the claims patentably distinct from the prior art. Accordingly, the amendments could not be considered tangentially related to the equivalent.

Finally, the Federal Circuit determined the equivalent was not “unforeseeable” at the time of the amendment. Unforeseeability is an objective standard based on what one of skill in the art would have found unforeseeable, not a subjective standard based on what the applicant actually foresaw. The Rudolph products accused of being “equivalent” to the claimed system would have literally infringed the claims as originally filed. Thus, by definition, the equivalent was not only objectively foreseeable, but was foreseen by ITC when it originally filed the patent claim. Accordingly, the unforeseeable exception also does not apply.

In the end, the Federal Circuit concluded that PHE applied, thereby preventing ITC from using the Doctrine of Equivalents in its infringement analysis.


The Federal Circuit made it clear that the exceptions to the presumption of PHE are narrow and difficult to prove. Patent applicants should operate under the assumption that any amendments made during prosecution are likely to be subject to PHE, so should only be made if necessary.

Moreover, if an amendment is made that is unrelated to patentability, applicants should consider stating that the amendment was made for reasons other than patentability so the prosecution history contains some support as to its purpose. This is no guarantee against the application of PHE, but it may provide a piece of evidence that weighs against presumptively applying PHE.