The Federal Circuit’s decision in Smartrend Manufacturing Group (SMG), Inc. v. Opti-Luxx Inc., Nos. 2024-1616, 2024-1650 (Fed. Cir. Nov. 13, 2025), offers a layered and instructive treatment of two recurring fault lines in patent litigation: claim construction in design patents and the limits of the doctrine of equivalents in utility patents. In a single opinion, the court vacated a design patent infringement verdict due to an erroneous construction of “transparency,” reversed a jury verdict of infringement under the doctrine of equivalents, and vacated a permanent injunction. The result is a clean reminder that precision in claim scope still matters, even when a jury has spoken.
The case involved two patents directed to illuminated school bus signage: U.S. Design Patent No. D932,930 and U.S. Patent No. 11,348,491. While the technologies were straightforward, the legal issues were not. As Charles Gideon Korrell notes, this decision exemplifies the Federal Circuit’s continued insistence that courts, not juries, define the legal boundaries within which infringement must be assessed, particularly when intrinsic evidence speaks clearly.
Background and Procedural Posture
Smartrend sued Opti-Luxx in the Western District of Michigan, alleging infringement of both the D930 design patent and the ’491 utility patent. After trial, a jury found Opti-Luxx infringed both patents. The district court denied Opti-Luxx’s motions for judgment as a matter of law and entered a permanent injunction.
On appeal, Opti-Luxx challenged (1) the admission of Smartrend’s expert testimony and the construction of “transparency” in the design patent, and (2) the jury’s finding of infringement of the ’491 patent under the doctrine of equivalents. Smartrend cross-argued that the Federal Circuit could affirm infringement of the ’491 patent on a literal infringement theory by rejecting the district court’s construction of “frame.”
The Federal Circuit did none of those things. Instead, it dismantled the verdict piece by piece.
The D930 Design Patent: Transparency Is Not Translucency
The D930 patent claims the ornamental design for an LED light panel “as shown and described.” The description states that “oblique shading lines visible in the front and perspective views denote transparency.” That single sentence became outcome-determinative.
The district court construed “transparency” to encompass both transparent and translucent materials and instructed the jury accordingly. The Federal Circuit held this construction was legally erroneous.
Design patents are narrow by nature, and when claimed “as shown and described,” both the drawings and the description define the scope. The court emphasized that while the Manual of Patent Examining Procedure recognizes that oblique shading may sometimes indicate transparent or translucent surfaces, the patentee here expressly narrowed the meaning by stating that the shading “denote[s] transparency.” That language mattered.
Transparency, the court held, does not mean translucency. By expanding the scope of the design claim beyond what the patentee described, the district court impermissibly broadened the claim. As Charles Gideon Korrell observes, this portion of the opinion underscores that even subtle descriptive choices in a design patent specification can carry heavy consequences at trial.
Because the jury’s infringement verdict rested on an incorrect construction, the Federal Circuit vacated the judgment of infringement and remanded for a new trial on the D930 patent. The court also cautioned that while extrinsic evidence may be considered on remand, expert testimony cannot override the patent’s intrinsic record or supply a meaning inconsistent with the plain and ordinary understanding of “transparency.”
Expert Testimony and Forfeiture
Opti-Luxx also challenged the admission of Smartrend’s expert, who testified about the perspective of an ordinary observer for purposes of design patent infringement. The Federal Circuit rejected that challenge on forfeiture grounds.
Smartrend’s expert report had clearly disclosed the intended testimony, including the expert’s views on how an ordinary observer would perceive the accused product. Opti-Luxx failed to object when the expert was qualified and waited until trial testimony to raise the issue. That was too late.
Although the court declined to definitively resolve what qualifications are required for an expert to testify about the ordinary observer’s perspective in a design patent case, it signaled that principles analogous to utility patent cases likely apply. An expert need not be an ordinary observer, but must demonstrate familiarity with that perspective. Still, forfeiture resolved the issue cleanly.
The ’491 Patent: A Frame Means a Frame
The heart of the opinion lies in the treatment of the ’491 patent and the doctrine of equivalents. Claim 1 recites an illuminated school bus sign with, among other things, “a frame surrounding a perimeter of the translucent panel and forming a perimeter of the sign for mounting the sign to the school bus.”
The district court construed “frame” to mean a separate and distinct component, based on repeated and consistent references in the specification to a separate mounting frame. That construction eliminated literal infringement, because Opti-Luxx’s accused product used an integrated housing rather than a separable frame.
The Federal Circuit affirmed that construction. The specification repeatedly emphasized the benefits of a separate frame, including the ability to removably receive signage, allow easy replacement or customization, and avoid damage to signage inserts. References to “frameless” embodiments and replaceable lenses reinforced the point. Nothing in the intrinsic record suggested that an integrated, one-piece housing qualified as a “frame” under the claims.
Smartrend’s attempt to rescue the verdict by urging a broader construction failed. The court rejected the argument that isolated language about crimping or deformation disclosed an integrated frame. Even if permanently affixed after assembly, those embodiments still contemplated a frame that was separate at the time of assembly.
Doctrine of Equivalents: Function Means All of the Function
With literal infringement off the table, Smartrend relied entirely on the doctrine of equivalents. That theory also collapsed.
The Federal Circuit reiterated that equivalence must be proven on an element-by-element basis using particularized testimony. Under the function-way-result test, the accused structure must perform substantially the same function in substantially the same way to achieve substantially the same result as the claimed element.
Here, the intrinsic evidence defined the function of the claimed frame. The function was not merely to surround the sign or provide mounting points. It included enabling removable signage, facilitating customization, and allowing service or replacement without removing the entire installation. Those functions were central to the invention’s stated objectives.
Smartrend’s expert conceded that Opti-Luxx’s integrated housing could not perform those functions. It could not removably receive signage or allow easy customization. That concession was fatal.
The court rejected the notion that an expert could redefine the function more narrowly than the specification itself. Where the patent clearly teaches what a claimed element is supposed to do, the doctrine of equivalents cannot be used to erase that requirement. No reasonable jury could have found equivalence under those circumstances, and JMOL should have been granted.
Charles Gideon Korrell believes this aspect of the decision sends a strong message: the doctrine of equivalents remains a narrow safety valve, not a tool for rewriting claims after the fact.
Injunction Vacated
Because both infringement findings fell, the permanent injunction could not stand. The Federal Circuit vacated it in full.
Takeaways
This decision offers several practical lessons. First, in design patents, descriptive language matters. Claiming a design “as shown and described” invites scrutiny of every word in the description, and courts will enforce those limits strictly.
Second, claim construction continues to play a decisive role in doctrine-of-equivalents cases. Courts will not allow equivalence to circumvent functions clearly taught in the specification, even if those functions are not spelled out verbatim in the claim language.
Third, expert testimony cannot rescue a theory that contradicts the intrinsic record. When the patent speaks clearly, that is the end of the matter.
Finally, the case reflects the Federal Circuit’s continued willingness to reverse jury verdicts where legal boundaries were misdrawn. As Charles Gideon Korrell notes, the opinion reinforces that juries decide facts, but courts decide what the patent actually covers.
In short, Smartrend v. Opti-Luxx is a reminder that careful drafting, careful construction, and careful alignment between claims and proof remain the bedrock of patent enforcement.