Is the Doctrine of Equivalents (DOE) dead, once again? Effectively, yes.

All an alleged infringer needs to do is raise an ensnarement defense (a claim that a DOE enlarged hypothetical claim reads on the prior art), and then show that the equivalent element was known in the prior art. Most equivalent elements (not considering other claim elements) are known in the art, which is why they are equivalent!

Under current CAFC precedent, all an alleged infringer has to do is offer some prior art. There is no burden on the alleged infringer to show that a DOE enlarged claim is either anticipated or obvious in view of the prior art. For example, if the equivalent element is presented in any prior art reference, the burden then shifts to the patent owner to prove patentability. But patentability cannot be proven. To do that, one would have to present all that is known in order to argue that the prior art does not disclose the invention. And, of course, this is impossible. Could one even begin to present all knowledge in order to show the absence of some knowledge? Certainly not.

That is why, outside of a DOE enlarged hypothetical claim, at either the U.S. Patent Office (PTO) or before any court, someone arguing a claim is invalid first has the burden of at least presenting a prima facie case of anticipation or obviousness. The burden then shifts to the one urging claim validity to refute the prima facie case. Outside of ensnarement, the concept of proving patentability simply doesn’t exist, and for good reason.

The CAFC’s current precedent regarding how to consider the validity of a doctrine of equivalents enlarged hypothetical claim (hereafter hypothetical claim) is summarized In JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC., 2016-1275, 2016-1575, decided: September 29, 2017.

The Court stated:

“The first step is “to construct a hypothetical claim that literally covers the accused device.” Next, prior art introduced by the accused infringer is assessed to “determine whether the patentee has carried its burden of persuading the court that the hypothetical claim is patentable over the prior art.” Emphasis added.

“The burden of producing evidence of prior art to challenge a hypothetical claim rests with an accused infringer, but the burden of proving patentability of the hypothetical claim rests with the patentee.” Emphasis added.

This precedent does not require the alleged infringer to do any more than merely present the prior art. It fails to require the alleged infringer to provide a prima facie case of anticipation or obviousness.

Before Jang, there was an acknowledgment that the hypothetical claim should be one that would have been allowed by the USPTO. “The pertinent question then becomes whether that hypothetical claim could have been allowed by the PTO over the prior art. WILSON SPORTING GOODS CO. V. DAVID GEOFFREY & ASSOCIATES, 904 F.2d 677 (1990).” But the CAFC has failed to recognize that this means the alleged infringer must then first provide a prima facie case of claim invalidity, as would be required at the PTO.

Thus, the Doctrine of Equivalents is for all intents and purposes dead.