Key Takeaways:
- Appropriate design patent claim construction may identify functional or utilitarian aspects of the design not dictated by function and acknowledge their ornamental appearance as part of the overall design;
- Rather than address prior art in claim construction, a district court might wait until a later stage to point out various features of the designs as they relate to the prior art where helpful to the jury or to explain the court’s analysis;
- U.S. design patent claims can include indeterminate dimensions and symbolic breaks in length; admission of indeterminate dimensions does not inherently indicate indefiniteness as the claim can be construed to maintain validity allowing for variation in length and width without altering the overall impression;
- Inconsistent use of broken lines does not inherently render a design patent invalid, rather, the errors must be material and of such magnitude that the overall appearance of the design is unclear.
On December 22, 2025, the U.S. District Court for the Southern District of New York (SDNY) issued a claim construction order addressing a design patent directed to artificial eyelash extension.
Plaintiff manufactures and sells artificial lash extensions and is the assignee of U.S. Patent No. D989,333, which includes a second set of figures “wherein the break lines indicate indeterminate length.”
The specification further states: [t]he broken lines consisting of evenly spaced lines in the in the figures show portions of the artificial lash extension that form no part of the claimed design. The break lines that separate parts of the artificial lash extension represent indeterminate length and form no part of the claimed design.
This type of broadening claim illustration and description is not uncommon in U.S. design patents – searching the USPTO Patent Public Search database for the term “indeterminate” in the specification reveals over 4700 issued design patents.
Nevertheless, during Examination, USPTO Examiners frequently to take issue with the word “indeterminate” and direct applicants to use language referring to a “symbolic break in length” rather than “indeterminate dimensions.” Searching the USPTO for “symbolic” identifies 5431 issued design patents, and shows emergence of the term, and shifting examination policy, between 2012 and 2013.
Now, a U.S. district court has weighed in and confirmed that illustration and description for indeterminate dimensions does not render a design patent claim indefinite.
Claim Construction
Design patent infringement analysis involves two steps: (1) the court first construes the claim to determine its meaning and scope; then (2) the fact finder then compares the properly construed claim to the accused design. Lanard Toys Ltd. v. Dolgenecorp LLC, 958 F.3d 1337, 1341 (Fed. Cir. 2020).
Design patents are typically claimed as shown in the drawings and claim construction is adapted accordingly. Egyptian Goddess, Inc. v. Swisa, Inc., 543 f.3d 665, 679 (Fed. Cir. 2008). It has been noted that “[w]ords cannot easily describe designs.” Sport Dimension, Inc. v. Coleman Co., 820 F.3d 1316, 1320 (Fed. Cir. 2020). The preferable course ordinarily will be for a district court not to attempt to construe a design patent claim by providing a detailed verbal description of the claimed design and instead allow the design to be represented by its illustration. Egyptian Goddess, Inc., 543 F.3d at 670.
Nevertheless, where a design contains both functional and non-functional elements, the scope of the claim must be construed to identify the non-functional aspects of the design as shown in the patent. Lanard Toys, 958 F.3d at 1342.
The district court noted that in Lanard Toys, the CAFC described a district court’s analysis as following its claim construction directives to a tee – meticulously acknowledging the ornamental aspects of each functional element and then considering the prior art, and that by highlighting aspects of the design without adopting a written construction, a court makes clear the key features of the design yet avoids the risk of improperly limiting the claim.
With this framing, the district court went on to reject the defendant’s overly detailed verbal claim constructions as contrary to the purpose of a design patent to protect the overall appearance, not individual features, and for creating requirements not present in the design patent’s drawings.
In line with CAFC guidance, the district court went on to assess the functional and ornamental features of the design patents to clarify their scope. The court concluded that the function of an artificial lash extension is to attach to the eye and enhance the aesthetic appearance of a person’s eyelashes. The court noted that the base of the design serves the functional purpose of holding the lashes together and providing a surface for attachment to the eye, and is already shown in broken lines to form no part of the claimed design. The court found that the lashes serve the aesthetic purpose of enhancing appearance, and there are innumerable ways to achieve the purpose.
Where neither party presented arguments regarding prior art references, the court declined to prematurely assess and noted it could, at a later stage, point out various features of the designs as they relate to the prior art where helpful to the jury or to explain the court’s analysis.
The claim construction order also involves a second design patent, without illustration for indeterminate dimensions, which was also construed without a lengthy verbal description, as well as two utility patents.
Validity
Defendant challenged validity of the asserted design patent, arguing that if the Court declines to adopt a verbal construction, the design patent is invalid as indefinite due to inconsistent use of break lines and discrepancies in the drawings.
The district court noted that assessing challenges to validity at this stage aids in claim construction, as “claims are generally construed so as to sustain their validity, if possible.” Whittaker Corp. v. UNR Indus., Inc., 911 F.2d 709, 712 (Fed. Cir. 1990).
To be valid, a patent must meet the requirement for definiteness under 35 U.S.C. §112.
In Nautilus, Inc. v. Biosig Instruments, 572 U.S. 898, 134 S. Ct. 2120, 189 L. Ed. 2d 37 (2014), the Supreme Court established the standard for definiteness for utility patents, holding that “a patent is invalid for indefiniteness if its claims, read in light of the specification delineating the patent, and the prosecution history, fail to inform, with reasonable certainty, those skilled in the art about the scope of the invention.”
For design patents, the definiteness requirement serves to “ensure that the disclosure is clear enough to give potential competitors (who are skilled in the art) notice of what design is claimed—and therefore what would infringe.” In re Maatita, 900 F.3d 1369, 1376 (Fed. Cir. 2018).
A design patent is indefinite if one skilled in the art, viewing the design as an ordinary observer, would not understand the scope of the design with reasonable certainty based on the claim and visual disclosure. Id. at 1376-77.
“A visual disclosure may be inadequate—and its associated claim indefinite—if it includes multiple, internally inconsistent drawings.” Id. at 1375.
“But errors and inconsistencies between drawings or the claim language do not merit a § 112 rejection if they do not preclude the overall understanding of the visual disclosure as a whole.” Deetsch v. Lei, 2024 U.S. Dist. LEXIS 202461, (S.D. Cal. Nov. 6, 2024) (citing In re Maatita, 900 F.3d at 1375-76).
Defendant argued that admission of “indeterminate length” indicates inherent indefiniteness, and that the break lines intersect the design at different points of the lashes or intersect different lashes across the patent drawings, rendering the design indefinite.
The district court disagreed, citing a 1995 CAFC decision finding indeterminate dimensions are not inherently indefinite (Alan Tracy, Inc. v. Trans Globe Imports, Inc., 60 F.3d 840 (Fed. Cir. 1995).
The court noted that the drawings with break lines, Figures 8 through 14, each have one vertical break line placed approximately at the middle of the drawing and one horizontal break line placed across the lashes, and that the break lines span the width and length of the figures.
Rather than interpreting the break lines to apply only to the portions of the lashes where they intersect, the district court concluded that the most natural reading of the break lines is that each of the lashes is of indeterminate length and width regardless of where the break line intersects the lash on the figure.
The district court understood that the break lines apply to the figure as a whole, and that the precise placement of the break lines on the figures does not change the claim of the drawings or render the drawing inconsistent.
Moreover, the district court found that acknowledgement that each of the lashes are of indeterminate length does not inherently render the patent indefinite.
As a design patent can only have one claim, the district court noted that Figures 8-14, by accounting for indeterminate length, cannot claim a different design than provided in Figures 1-7, therefore any variation in the lengths or placement of the lashes allowed by the break lines would need to comport with the overall appearance of the design as provided in the initial seven figures.
The district court reasoned that to the extent that the break lines could be read to include lashes of any length, width and size relative to one another, and thus greatly expand the scope of the design, that level of indefiniteness can be resolved by construing the design more narrowly, citing Microprocessor Enhancement Corp, 520 F.3d at 1376 (“‘[A] claim that isamenable to construction is not invalid on the ground ofindefiniteness’ if the construction renders the claimdefinite.”) (quoting Energizer Holdings, Inc. v. Int’l Trade Com’n, 435 F.3d 1366, 1371 (Fed. Cir. 2006)).
Therefore, the court construed the break lines to allow for slight variation in the length and width of each lash and the spacing between them, provided these variations do not alter the overall impression of the design.
“By allowing for variation, this construction aligns with the purpose of design patents: rather than covering only designs that match the patent drawings with mathematical precision, the patent protects the “overall appearance” of the design, as seen by an ordinary observer.”
Defendant also argued that inconsistent use of broken lines rendered the claim indefinite, but the district court disagreed, stating that inconsistent use of broken lines does not inherently render a design patent invalid, rather, the errors “must be material and of such magnitude that the overall appearance of the design is unclear.” Apple, Inc. v. Samsung Elecs. Co., 932 F. Supp. 2d 1076, 1085-86 (N.D. Cal. 2013); HR U.S. LLC v. Mizco Int’l, Inc., 2009 U.S. Dist. LEXIS 27056, (E.D.N.Y. Mar. 31, 2009); Times Three Clothier, LLC v. Spanx, 2014 U.S. Dist. LEXIS 59448, (S.D.N.Y. Apr. 29, 2014).
The district court concluded that the sole inconsistency in Figure 7 compared to other corresponding views would not preclude a person of ordinary skill in the art from understanding the overall appearance of the design.
Litigation in the case continues – Lashify, Inc. v. Quingdau Net. Tech. Co., 25-cv-4183 (SDNY).
George Raynal
george.raynal@designlawgroup.com
Meera Kamath
