Reaffirming the narrow application of the tangential relationship exception to the Festo presumption of prosecution history estoppel, the U.S. Court of Appeals for the Federal Circuit reversed a finding of infringement under the doctrine of equivalents. Cross Medical Products, Inc. v. Medtronic Sofamor Danek, Inc., Case No. 05-1415 (Fed. Cir., Mar. 20, 2007) (per curiam) (Rader, J., concurring).
In an earlier decision in this litigation, the district court ruled that Medtronic’s polyaxial screws literally infringed Cross Medical’s U.S. Patent No. 5,474,555 (the ’555 patent). Medtronic then redesigned its polyaxial screws to avoid the claimed "thread depth" recitation that required threads extending below the top of the claimed rod. Medtronic replaced the corresponding threads with an undercut.
Cross Medical subsequently accused Medtronic’s redesigned products of infringement under the doctrine of equivalents. Medtronic argued that under principles of prosecution history estoppel, Cross Medical should be precluded from so doing. Prosecution history estoppel prevents a patentee from recapturing under the doctrine of equivalents subject matter surrendered during prosecution to obtain a patent. During the prosecution of the ’555 patent, the patentee responded to a rejection under § 112 by amending its claim 5 to include the "thread depth" requirement, thereby gaining allowance of the application.
Under Festo, this narrowing amendment creates a presumption of prosecution history estoppel which can be rebutted, inter alia, by demonstrating (as Cross Medical argued here) that the alleged equivalent was unforeseeable at the time of the amendment or that the alleged equivalent was only tangentially related to the amendment. The district court found that under the tangential relationship test, the presumption of prosecution history estoppel was successfully rebutted and determined that the redesigned products infringed under the doctrine of equivalents. Medtronic appealed.
The Federal Circuit began its analysis by reaffirming "the principle that the tangential relation criterion for overcoming the Festo presumption is very narrow" and "an amendment made to avoid the prior art that contains the equivalent in question is not tangential." The Court concluded that the narrowing amendment excludes the accused equivalent that does not include the recited "thread depth" limitation added by amendment. On that basis the Court held the design-around was not captured under the doctrine of equivalents (as the equivalent required to do so related directly to the amendment) and ruled that Cross Medical could not overcome the Festo estoppel presumption and invoke the doctrine of equivalents.
In a concurring opinion, Judge Rader called into question whether the tangential relationship exception will ever be used successfully again. Rader expressed his view that the tangential exception "exacerbate[s] the policy deficiencies of the doctrine of equivalents" since "[u]pon invoking tangentiality, the patentee has already admitted that the equivalent falls within the scope of surrendered subject matter."
In Judge Rader’s view, the tangential relationship exception undermines the public notice of claims. He cited Medtronic’s deliberate design-around as an example. Even though Medtronic considered the prosecution history of the ’555 patent in connection with its redesign, the prosecution history will not (itself) address a "tangential" equivalent as a patentee will ordinarily attempt to explain any narrowing amendment in such a way as to narrow the tangential relationship exception and thereby attempt to preserve the broadest possible scope of equivalents. In Judge Rader’s view, if, in review of the prosecution history, the public reasonably believes that the subject matter that was surrendered during prosecution is part of the public domain, the tangential relationship exception to the estoppel presumption should not apply.
Practice Note: The Federal Circuit reiterated that U.S. law encourages design-arounds, as they bring a steady flow of innovations to the marketplace. Cross Medical illustrates the benefits and utility of a properly calculated redesign effort. Judge Rader’s views echo the original Federal Circuit Festo "brightline" rule and put new pressure on parties attempting to invoke the doctrine of equivalents.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.