Federal Circuit Props Door Open for Doctrine of Equivalents

September 5, 2014

Turhan F. Sarwar

What This Means to You

  • Don’t relegate equivalence theories to the backburner—develop arguments regarding equivalence using facts and expert testimony with an eye towards presenting the theory (or an argument about why the theory fails) to a jury.


In EPOS Techs. v. Pegasus Techs., the U.S. Court of Appeals for the Federal Circuit (Federal Circuit) confirmed the longstanding role of patent specifications and preferred embodiments in claim construction, holding that the district court either improperly imported limitations from the patent specifications or adopted constructions that improperly excluded a preferred embodiment. Near the end of its opinion, the Federal Circuit also vacated the district court’s two-sentence summary judgment denial of the patent owner’s doctrine of equivalents argument and remanded for reconsideration.

While this latter analysis is tucked away into just two pages, it should be considered a signal to take the doctrine of equivalents seriously. The Federal Circuit criticized the district court for shortcutting its equivalence analysis to a “binary choice” and failing to consider the function of the accused products and expert testimony offered by the patent owner. In doing so, the Federal Circuit held that a court must “thoroughly consider[] whether a reasonable jury could conclude” that certain features are equivalent to claim limitations. 

Case Background

In 2007, EPOS Technologies Ltd. (EPOS) filed a complaint against Pegasus Technologies Ltd. for declaratory judgment of noninfringement of four patents. Pegasus asserted two additional patents in its counterclaims. After claim construction, the district court granted summary judgment of noninfringement. For one of the patents—the ’371 patent—noninfringement was granted under the doctrine of equivalents.

Pegasus’s ’371 patent claimed an electronic drawing implement that could receive or transmit an “intermittent” ultrasound signal. It was undisputed that EPOS products generate a “continuous” ultrasound signal. The district court, in a very brief discussion, concluded that holding continuous ultrasound signals to be equivalent to the claimed “intermittent” ultrasound signal would “eliminate the intermittent limitation entirely.”

Pegasus appealed various portions of the district court’s order, including the court’s grant of summary judgment under the doctrine of equivalents.

Decision Analysis

The Federal Circuit balked at the brevity of the district court’s equivalence analysis, noting that the lower court “devoted only two sentences to its decision on infringement of the ’371 patent …” The Federal Circuit emphasized that the district court must do more, “ask[ing] whether an asserted equivalent is an ‘insubstantial difference’ from the claimed element, or whether it matches the ‘function, way, and result of the claimed element.’” The Federal Circuit cautioned against “shortcut[ting] this inquiry by identifying a ‘binary’ choice in which an element is either present or ‘not present.’”

The district court’s brief analysis did just that. The Federal Circuit pointed out that the evidence in front of the district court had not compelled an easy, binary choice between “intermittent” and “continuous.” Instead, the Federal Circuit suggested that the decision needed to take into account “the functioning of the EPOS products” and “Pegasus’s expert declaration explaining why the EPOS Products’ signals are equivalent to the claimed intermittent ultrasound signal.”


The Federal Circuit’s rejection of “shortcut” doctrine of equivalents analysis signals that the doctrine is alive and well, and can be a viable tool for plaintiffs. It should also be dealt with seriously by defendants.

The Federal Circuit made clear that a district court must carefully consider any doctrine of equivalents evidence presented to it—including evidence regarding the functionality of the accused products and expert testimony offered regarding equivalence. After considering this evidence, the district court must determine whether a reasonable jury could conclude that product features are equivalent to claim limitations.

Patent owners should thus invest time in developing such theories (if available) with factual support and expert testimony, with an eye towards presenting the theory in front of a jury. Accused infringers should develop their theories against the doctrine of equivalents with the same diligence.