Plaintiff’s Refusal To Articulate A Hypothetical Claim Warrants Summary Judgment Of Noninfringement Under The Doctrine Of Equivalents
On January 28, 2021, the U.S. District Court for the Northern District of California (NDCA) issued an order granting summary judgment of noninfringement under the doctrine of equivalents. Fluidigm Corp. v. IONpath, Inc., Case No. 3:19-cv-05639-WHA, Dkt. No. 210 (N.D. Cal. Jan. 28, 2021). The NDCA found that the patentee “abdicated” its burden under the doctrine of equivalents by refusing to engage in the hypothetical claim analysis required under defendant’s ensnarement defense.
As background, a product that does not literally infringe may still infringe under the doctrine of equivalents if it (1) performs the same function, (2) in the same way, (3) and with the same result as the asserted claim. The ensnarement defense limits the effects of this doctrine by barring patentees from asserting an equivalent that “ensnares” the prior art. When a defendant invokes the ensnarement defense, the parties must engage in a hypothetical claim analysis in which the patentee articulates a hypothetical claim that covers the accused product, and the defendant produces prior art to challenge such hypothetical claim. The patentee then bears the burden of proving that its hypothetical claim does not cover the defendant’s prior art.
On September 6, 2019, Fluidigm Corporation (Plaintiff) filed a complaint against IONpath, Inc. (defendant) in the NDCA alleging infringement of three patents relating to mass cytometry methods and systems for cell structure and biomarker analysis. In August 2020—in the midst of expert discovery—plaintiff was granted leave to amend its infringement contentions with its backup doctrine of equivalents theories in response to defendant’s proposed claim constructions. In November 2020, the parties cross-moved for partial summary judgment; plaintiff moved for summary judgment that, in relevant part, certain asserted claims were valid and infringed under the doctrine of equivalents, and defendant moved for summary judgment that the same claims were invalid and not infringed, including because plaintiff abdicated its burden under the ensnarement doctrine. The NDCA granted defendant’s motion.
The NDCA rejected plaintiff’s argument that it was not required to identify a hypothetical claim until after Defendant identified specific prior art. Citing the Federal Circuit’s opinion in Jang v. Boston Science Corporation, the NDCA held that the hypothetical claim analysis begins with the patentee’s articulation of a hypothetical claim. Citing the Federal Circuit’s opinion in Wilson Sporting Goods v. David Geoffrey & Associates, the NDCA further held that the step of identifying a hypothetical claim is a necessary step in advancing plaintiff’s doctrine of equivalents infringement theories. Because plaintiff refused to identify a hypothetical claim for more than a year, the NDCA found that it had disclaimed this necessary step and, by extension, its doctrine of equivalents infringement theories altogether.