"Smartrend Manufacturing Group (SMG), Inc. v. Opti-Luxx Inc., No. 2024-1616 (Fed. Cir. Nov. 13, 2025). Writing for a unanimous panel, Judge Dyk reversed a jury verdict finding that Opti-Luxx's illuminated school bus sign infringed SMG's U.S. Patent No. 11,348,491 under the doctrine of equivalents. The appellate court held that no reasonable jury could find the accused product's frame performed the same function as that claimed."
"The basic rule here is that the fact finder should first look to the patent's written description and specification to determine the function of a claimed element. But, if (only if) the patent is silent or ambiguous on the function, then turn to the perspective of one of ordinary skill in the art via extrinsic evidence such as expert testimony."
"Almost everyone is a bit uncomfortable with the DoE. Almost by definition, the doctrine only arises when the infringer is doing something different than what is claimed in the patent. I.e., they don't literally infringe what has been claimed. With the DoE, they might be tagged for doing something close enough - but where is that fuzzy threshold? The discomfort with this fuzziness has led the courts to develop various mechanisms to cabin-in the DoE to avoid overreach."
The Federal Circuit reversed a jury verdict finding Opti-Luxx infringed SMG's patent under the doctrine of equivalents, holding the accused frame did not perform the same function as claimed. The fact finder must first consult the patent's written description and specification to identify an element's function. Only when the specification is silent or ambiguous should extrinsic evidence reflecting one of ordinary skill in the art be used. The doctrine of equivalents addresses non-literal differences, creating a fuzzy threshold that courts constrain with mechanisms like summary judgment and JMOL. The leading test remains the element-by-element function-way-result analysis.
Read at Patently-O
Unable to calculate read time
Collection
[
|
...
]