The patentee sued alleging infringement of a patent directed to a coronary stent. A jury found that there was no literal infringement but determined that the accused product infringed under the doctrine of equivalents. The patentee’s motion for judgment as a matter of law (JMOL) regarding literal infringement was denied. Post-trial, the district court held a hearing on the accused infringer’s ensnarement defense. The court determined that the patentee was unable to construct a proper hypothetical claim, declined to conduct further ensnarement analysis, and vacated the jury’s finding of infringement under the doctrine of equivalents. The patentee appealed.

The Federal Circuit affirmed the district court’s denial of JMOL regarding literal infringement, finding that there was substantial evidence to support the jury’s finding that the accused device did not literally infringe. Specifically, the jury heard sufficient evidence that: (1) the relevant components of the accused stent expanded when the stent expanded, whereas the claimed element of the stent did not expand; and (2) the relevant components of the accused stent were joined together in “peak-to-valley” formation, rather than a “peak-to-peak” formation as the claims required.

Regarding ensnarement, the Federal Circuit held that a district court considering an ensnarement defense can find in favor of the accused infringer if the patentee is unable to provide an adequate hypothetical claim. The Federal Circuit agreed that the patentee’s first hypothetical claim impermissibly included a narrowing limitation. The Federal Circuit further agreed that the language the patentee added to his second hypothetical claim did not change the scope of the original claim so as to encompass the accused product. The Federal Circuit held that the district court was not required to construct hypothetical claims on the patentee’s behalf or conduct further analysis to determine if the hypothetical claims ensnared the prior art. The Federal Circuit noted that a patentee “bears the burden of proving that it is entitled to the range of equivalents which it seeks.” Because he could not construct an adequate hypothetical claim, patentee failed to meet his burden of proving that his doctrine of equivalents theory did not ensnare the prior art; thus, the jury verdict was properly vacated.