Similarity to Product That Literally Infringes Patent is Sufficient to Support Doctrine of Equivalents Verdict

In the non-precedential decision WCM Industries Inc. v. IPS Corp., the Federal Circuit overturned the district court’s grant of IPS’s motion for judgment as a matter of law, finding that the patentee WCM provided sufficient evidence to support the jury’s finding of infringement under the doctrine of equivalents based on one product’s similarity to another, literally-infringing product.

The case involves infringement of WCM’s patents relating to a bathtub overflow assembly that eliminates leaks and is easier to install over conventional overflow devices. The representative claim, claim 12, recites an overflow pipe, a lip extending radially outwardly from an outer surface of the overflow pipe, and a nut element. The nut element includes a threaded portion that is compatible with threads of the overflow pipe, and the nut element includes an outer periphery with a series of radially extending lugs (see item 92 in Fig. 4 below) that detachably engage an inner surface of a cap (96) that fits over the nut.


IPS bought the assets of American Brass and Aluminum Foundry Company (AB&A) and continued to sell AB&A’s overflow product (referred to as the “Classic Product”). The Classic Product included a locknut having six angular high points around the circumference of the locknut, as well as curved finger indentations (see first image below). In 2014, after WMC filed its Complaint in the Western District of Tennessee, IPS revised the Classic Product by modifying the locknut to remove the finger indentations (see second image below).

At trial, the jury found that the Classic Product literally infringed and that the Revised Product infringed under the doctrine of equivalents. The district court, however, granted IPS’s post-trial motion that the Revised Product did not infringe under the doctrine of equivalents, finding that WCM failed to present opinion testimony on infringement and none of the evidence introduced at trial was sufficient to prove infringement under the doctrine of equivalents. The district court also left in place the jury’s finding that the infringement was willful, and awarded treble damages.

In the opinion authored by Judge Prost, the Federal Circuit reversed and held that a reasonable jury could have found that the “lugs” limitation was satisfied under the doctrine of equivalence based on the evidence. The panel noted that a finding of equivalence does not require opinion testimony, much less expert opinion testimony. In addition, the record included testimonial evidence of the similarity between the installation of the Classic Product and the Revised Product, and that both locknuts were interchangeable with WCM’s commercial product. The court dismissed IPS’s argument that this testimony was insufficient because it did not compare the accused products to the claims. Instead, the court found that the comparison of the Revised Product to (1) the Classic Product that was found to literally infringe and (2) the WCM commercial product were sufficient to support the jury’s finding of infringement under the doctrine of equivalents.

The panel also affirmed the district court’s decision with respect to willful infringement, although it vacated the award of treble damages and found that the district court improperly applied the enhancement analysis factors set forth in Read Corp. v. Portec Inc.

The panel’s willingness to overturn the district court and reinstate the jury’s finding of infringement offers hope for the doctrine of equivalents, but the decision appears to be limited to its specific facts. The opinion carefully pointed out that the technology at issue was straightforward, the claim language was readily understandable, and only one claim limitation was in dispute between the parties. Nevertheless, parties may be able to rely on product comparisons in similar cases when the relative simplicity of the case permits.

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