1. What the Patent Owner Must Establish at Trial
The patent owner bears the burden of proving infringement by a preponderance of the evidence, meaning more likely than not. Visual similarity addresses whether the accused product falls within the claimed design. Under 35 U.S.C. § 271(a), direct infringement also requires an unauthorized act, such as making, using, selling, offering to sell, or importing the patented invention. The patent term and territorial requirements matter.
Begin with the Issued Patent and Its Claim
Use the issued drawings, written description, and prosecution history to identify the asserted claim. Comparing retail products alone can mislead because a commercial product may include unclaimed features. Solid lines generally depict the claimed design, while broken lines commonly identify unclaimed surroundings or boundaries. Read the patent's explanation before selecting the claimed portions. Broader protection issues appear in our design patent guidance.
Apply the Observer Standard to the Overall Design
The ordinary observer considers the overall ornamental appearance with the attention a purchaser usually gives. The hypothetical observer knows relevant prior designs. Clearly dissimilar designs can fail the test without a detailed prior-art comparison. Where similarity makes the issue closer, relevant prior art supplies context for deciding whether differences matter. A matching curve alone does not establish the overall resemblance.
2. Building Visual Comparisons That the Court Can Evaluate
Complete views help the court compare the designs without guessing about missing surfaces. Assemble corresponding front, rear, side, and perspective views where the patent includes them. CAD models and a fixed number of photographs are not mandatory.
Match Views without Changing Proportions
Use corresponding angles and consistent lighting that preserves visible contours. Resizing can help, but stretching images alters proportions. Label figure numbers and product models clearly, and retain uncropped originals. Keep annotations separate from source images, and use overlays only to supplement complete views.
Use Physical Samples and Renderings for Different Purposes
A physical sample can show surfaces or depth that a listing photograph conceals. Record which sample was photographed, and explain whether a CAD rendering comes from manufacturer files or later reconstruction. Support a reconstruction's accuracy with the actual product. Preserve the sample before destructive inspection, and document changes caused by testing.
Address Functionality without Erasing the Product
Design patents protect ornamental appearance, not functional utility. A component can have both functional and ornamental aspects, so deleting an entire handle from comparison may distort the claim. Claim construction identifies the protected ornamental aspects while accounting for functionality. Solid lines do not establish that an element is necessarily ornamental.
3. Preserving the Product, Its Source, and the Sales Record
An image alone may not identify who supplied the product or when. Preserve evidence connecting the accused model to the defendant and the alleged infringing conduct. Record the transaction, product version, and responsible party. Our patent infringement litigation overview
Document Purchases and Online Listings
Keep receipts, order confirmations, shipping labels, packaging, and model identifiers with the purchased sample. Save relevant listings with their URLs, capture dates, seller names, and available product images. Shared listing photographs may not identify what a particular seller supplied. Keep separate records for different product versions.
Establish Authenticity and Preserve Original Files
Federal Rule of Evidence 901 generally requires sufficient support that an exhibit is what its proponent claims. A purchaser or photographer with personal knowledge may help establish that foundation. Retain original files, metadata, and capture records so screenshots remain traceable. Webpage statements may also raise hearsay questions depending on their use.
Preserve Relevant Material When Litigation Is Anticipated
Reasonably anticipated litigation can trigger a duty to preserve relevant evidence before a complaint is filed. Preserve relevant samples and electronic records, suspending routine deletion where appropriate. Federal Rule of Civil Procedure 37(e) addresses certain losses of electronically stored information that should have been preserved. If interim relief is contemplated, the same preservation effort can support a motion for preliminary injunction
4. Frequently Asked Questions
Generally, intentional copying is not required to establish direct infringement under § 271(a). Independent development therefore does not by itself defeat an otherwise proven direct infringement claim. Copying may matter to other issues, but allegations of copying cannot replace proof that the accused appearance falls within the claim.
Neither is automatically required in every case. An expert may assist with prior art or technical evidence, but the ordinary observer remains the governing perspective. A survey must measure a relevant issue using defensible methods. Actual customer confusion is not a separate mandatory element, and expert evidence must satisfy Federal Rule of Evidence 702 before admission.
06 Oct, 2026
