An evidence of use (EoU) chart is a claim chart that maps each element of a patent claim onto public evidence that a specific product has that element. Every row cites the page, figure or screenshot that shows the match. Patent owners use them in licensing talks and litigation, as described on the page on EoU claim charts.
What an evidence of use chart shows
The chart shows, for each claim element, where the accused product has it. Under 35 U.S.C. 271(a), whoever without authority makes, uses, offers to sell or sells a patented invention in the United States, or imports it, during the term of the patent infringes it. Literal infringement needs every element of the claim, so the chart has one row for each clause.
It is one of three main chart types, set side by side in the guide to claim charts. Its evidence describes a current product, not an earlier publication.
Where product evidence is found
Most evidence of use comes from what the seller publishes about its own product. The common sources are:
- user manuals, installation guides and datasheets;
- product pages, catalogues and demonstration videos;
- developer documentation, release notes and open-source code;
- technical papers and conference talks by the seller’s engineers;
- regulatory records, such as the Federal Communications Commission (FCC) FCC ID search for radio devices and the 510(k) database of the US Food and Drug Administration for medical devices;
- teardown reports and tests on a purchased sample.
Regulatory records are often missed, although a radio device sold in the US usually carries an FCC ID on its label or screen, and that code leads to its authorisation record.
How the EoU search is run
The search starts from the claim, not from the product. A typical sequence is:
- The claim is split into elements, and terms whose meaning may be disputed are noted.
- Target products are named by the client or found by searching for the claimed feature.
- Each source is collected and a copy is kept.
- Each element is mapped to the strongest citation.
- The date of each source and the product version it describes are recorded.
- Rows where the match is partial or assumed are flagged.
A claim may recite a “wireless transceiver module” while the manual says “Bluetooth chip”, so the row explains why the two terms are treated as the same. Firms that prepare evidence of use claim charts usually deliver the source files too.
Documenting evidence in the chart
The rows below are an invented illustration and do not describe a real project.
| Claim element | Evidence | Source and date | Comment |
|---|---|---|---|
| [1a] a housing with a removable cover | Manual figure shows the cover held by two clips | User manual, captured March 2026 | Literal match |
| [1b] a sensor that measures ambient temperature | Datasheet lists an “environment sensor” | Datasheet, revision C, dated January 2026 | Weak: the measured quantity is assumed |
Screenshots carry the full URL and the capture date. Web pages change, so a copy is also saved in a public archive, such as the Internet Archive, or as a dated PDF.
Dating the evidence of use
The date of each source matters for damages as much as for infringement. Under 35 U.S.C. 286, no damages are recovered for infringement committed more than 6 years before the complaint or counterclaim is filed. Evidence that the feature existed early in that window is worth more than a current brochure, provided the patent had issued by then. Marking and notice rules can shorten the period.
Under 35 U.S.C. 287(a), where patented products are sold unmarked, damages are recovered only for infringement after the infringer was notified and continued to infringe. Filing a suit counts as notice. Where the rule applies, a notice letter that names the specific product and charges it with infringement can start the damages period, and an attached chart shows that the charge is specific.
When public evidence is not enough
Some elements sit inside the product, in firmware, a circuit or a chemical composition, and no document describes them, so the chart marks the gap.
The options are a test purchase and a reverse engineering study, or a different claim that public evidence supports. Before filing in a US court, counsel certifies under Rule 11 of the Federal Rules of Civil Procedure that the factual contentions have evidentiary support, after a reasonable inquiry. A chart with sourced and dated rows is one way to document that inquiry, as the post on invalidity contentions and Rule 11 claim charts explains.
Evidence of use charts from Synoptic IP
We prepare evidence of use charts with sourced, dated and archived citations for law firms and licensing teams. Send the patent and the target products through our evidence of use claim chart service.
This guide is general information and is not legal advice.
Frequently Asked Questions
What is evidence of use in a patent?
Evidence of use is public material showing that a product has each element of a patent claim, such as manuals, datasheets, product pages, source code and teardown results. It is arranged in a chart, one claim element per row, with a citation showing where each element appears.
Is an EoU chart the same as an infringement claim chart?
Yes, in most usage, both terms describe a chart that maps a patent claim onto an accused product. EoU chart is common in licensing work, while infringement claim chart or infringement contentions are the usual terms once a case has been filed in a US court.
Can website screenshots be used as product evidence?
Yes, screenshots are widely used, provided each one shows the full URL and the capture date. Pages change, so an archived copy or a dated PDF helps show what the page said on that day. The attorney decides how the evidence is later authenticated in court.
How many products go into one EoU chart?
Usually one product, or one family of products that share the claimed feature, goes into each chart. Where models differ in that feature, a separate chart for each model avoids rows that are true for one version and false for another.
How much does an EoU chart cost?
The cost depends on the number and length of the claims, how much public evidence exists, whether a teardown or translation is needed and the deadline. Charts are usually priced per chart, one patent against one product, so a quote follows a first look at the patent and target.