To succeed on a doctrine of equivalents theory, the patentee must demonstrate equivalence [which] will be more difficult when the accused structure has an element that is the opposite of the claimed element, especially where the specification or prosecution history highlights the differences.

On February 20, 2013, in Brilliant Instruments, Inc. v. GuideTech, Inc., the U.S. Court of Appeals for the Federal Circuit (Dyk, Moore,* Reyna) reversed and remanded the district court's summary judgment that Brilliant did not infringe U.S. Patents No. 6,226,231, No. 6,091,671 and No. 6,181,649, which related to circuits that measure the timing errors of digital signals in high-speed microprocessors. The Federal Circuit stated:

We agree with GuideTech [that] the district court erred when it granted summary judgment that Brilliant does not infringe under the doctrine of equivalents. To find infringement under the doctrine of equivalents, any differences between the claimed invention and the accused product must be insubstantial. One way of proving infringement under the doctrine of equivalents is to show, for each claim limitation, that the accused product "performs substantially the same function in substantially the same way with substantially the same result as each claim limitation of the patented product."

In this case, GuideTech submitted an expert report by Dr. West that detailed its doctrine of equivalents theory under the function-way-result test. Brilliant does not contest Dr. West's recitations of the function, way, and result of the asserted claims or the accused products. Nor does Brilliant provide any contrary evidence. Instead, it argues that GuideTech's doctrine of equivalents infringement theory vitiates the requirement that the claimed "first current circuit" and the "capacitor" are separate claim elements. Brilliant's vitiation argument fails. . . . "Vitiation" is not an exception to the doctrine of equivalents, but instead a legal determination that "the evidence is such that no reasonable jury could determine two elements to be equivalent." The proper inquiry for the court is to apply the doctrine of equivalents, asking whether an asserted equivalent represents an "insubstantial difference" from the claimed element, or "whether the substitute element matches the function, way, and result of the claimed element." If no reasonable jury could find equivalence, then the court must grant summary judgment of no infringement under the doctrine of equivalents. The vitiation concept has its clearest application "where the accused device contain[s]the antithesis of the claimed structure." This makes sense; two elements likely are not insubstantially different when they are polar opposites. "Courts should be cautious not to shortcut this inquiry by identifying a 'binary' choice in which an element is either present or 'not present.' Stated otherwise, the vitiation test cannot be satisfied by simply noting that an element is missing from the claimed structure or process because the doctrine of equivalents, by definition, recognizes that an element is missing that must be supplied by the equivalent substitute." The vitiation test cannot be satisfied merely by noting that the equivalent substitute is outside the claimed limitation's literal scope. Rather, vitiation applies when one of skill in the art would understand that the literal and substitute limitations are not interchangeable, not insubstantially different, and when they do not perform substantially the same function in substantially the same way, to accomplish substantially the same result. In short, saying that a claim element would be vitiated is akin to saying that there is no equivalent to the claim element in the accused device based on the well-established "function-way-result" or "insubstantial differences" tests.

To succeed on a doctrine of equivalents theory, the patentee must demonstrate equivalence under one of these two tests. This will be more difficult when the accused structure has an element that is the opposite of the claimed element, especially where the specification or prosecution history highlights the differences. If the claimed and accused elements are recognized by those of skill in the art to be opposing ways of doing something, they are likely not insubstantially different. The concept of vitiation is an acknowledgement that each element in the claim must be present in the accused device either literally or equivalently. And we have applied this concept to cases where we have recognized that two alternatives exist that are very different from each other and therefore cannot be equivalents for infringement purposes.

Applying these concepts to the facts of this case, we conclude that summary judgment must be reversed. The element at issue is: "wherein said shunt and said capacitor are operatively disposed in parallel with respect to said first current circuit." Dr. West, GuideTech's expert, agreed that in the accused device, the measurement capacitor is a component of the first current circuit. While this disposes of literal infringement, the doctrine of equivalents inquiry is: did GuideTech create a genuine issue of material fact regarding whether Brilliant's capacitor, located within the first current circuit, performs substantially the same function in substantially the same way to achieve substantially the same result as the claimed capacitor, which is operatively disposed in parallel to the shunt? Everyone agrees that the capacitor in the accused device is not located in exactly the same place as the claimed capacitor, but is the change in location an insubstantial difference? We conclude that, viewing all factual inferences in favor of GuideTech, it has created a genuine issue of material fact which precludes summary judgment.