What a Patent Infringement Claim Chart Must Show, and How AI-Drafted Charts Can Be Checked

A patent infringement claim chart is a table that maps each limitation of an asserted patent claim to the place in an accused product, process or other instrumentality where the patentee says that limitation is found. In district courts with patent local rules, it forms part of the patentee's infringement contentions. The Northern District of California's Patent L.R. 3-1(c) requires “a chart identifying specifically where and how each limitation of each asserted claim is found within each Accused Instrumentality.” Trial-court coverage is on the Litigation hub.

What must infringement contentions under Patent L.R. 3-1 include?

Under the Northern District of California's Patent Local Rules, revised on 11 August 2026, the contentions must identify each asserted claim and each accused instrumentality and chart, for each pairing, specifically where and how every limitation is found and whether it is present literally or by equivalents. The patentee serves this disclosure, separately for each opposing party, not later than 14 days after the Initial Case Management Conference (Patent L.R. 3-1).

The chart sits inside a longer disclosure. Rule 3-1(a) requires each allegedly infringed claim with the subsections of 35 U.S.C. § 271 asserted, and 3-1(b) each accused instrumentality, identified “as specific as possible,” products “by name or model number, if known.” Rules 3-1(d) and (f) to (i) cover indirect infringement, priority dates, the patentee's own practising products, damages timing and any willfulness allegation.

Two kinds of row need more than a location. For a limitation the patentee contends is governed by 35 U.S.C. § 112(6), the means-plus-function provision now codified as § 112(f), Rule 3-1(c) requires “the identity of the structure(s), act(s), or material(s) in the Accused Instrumentality that performs the claimed function”; the explainer on Williamson v. Citrix covers when a limitation falls under that provision. For a limitation said to be met by equivalents, Rule 3-1(e) requires the specific portion of the accused instrumentality and how it is “insubstantially different from the claim limitation,” for example under the function/way/result test.

Why does a claim chart go limitation by limitation?

Because infringement is assessed element by element. In Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997), No. 95-728, a unanimous Supreme Court, in an opinion by Justice Thomas, wrote that “[e]ach element contained in a patent claim is deemed material to defining the scope of the patented invention,” and so “the doctrine of equivalents must be applied to individual elements of the claim, not to the invention as a whole.” (Id. at 29.)

The Court added that the doctrine, “even as to an individual element,” may not be allowed “such broad play as to effectively eliminate that element in its entirety” (at 29). It framed the essential inquiry as: “Does the accused product or process contain elements identical or equivalent to each claimed element of the patented invention?” (At 40.) A chart built on that question has a row per limitation: for an abstract claim reciting elements A, B and C, three rows, each stating where and how the element is met, literally or by equivalents. The explainer on how to read a patent covers breaking a claim into its limitations.

How does the Eastern District of Texas rule differ?

Its wording is close but not identical. Under E.D. Tex. P.R. 3-1, the disclosure is due “[n]ot later than 10 days before the Initial Case Management Conference with the Court,” and P.R. 3-1(c) asks for a chart identifying “specifically where each element of each asserted claim is found within each Accused Instrumentality,” without the Northern District's “and how.” P.R. 3-1(d) asks whether each element is present literally or by equivalents, without the further explanation that the Northern District's Rule 3-1(e) requires.

Can infringement contentions be amended?

Yes, within limits. Northern District Patent L.R. 3-6 permits amendment “only by order of the Court upon a timely showing of good cause” and lists examples that may support good cause absent undue prejudice, among them a claim construction different from any party's proposal and recent discovery of nonpublic information about the accused instrumentality despite diligent efforts. It adds: “The duty to supplement discovery responses does not excuse the need to obtain leave of court to amend contentions.” In the Eastern District of Texas, P.R. 3-6(a)(1) allows amended contentions without leave within 30 days after the claim construction ruling if the patentee believes in good faith that the ruling requires them; otherwise good cause is needed.

The Federal Circuit addressed an earlier version of the Northern District rules in O2 Micro International Ltd. v. Monolithic Power Systems, Inc., 467 F.3d 1355 (Fed. Cir. 2006), No. 2006-1064, in an opinion by Judge Dyk. It held that Federal Circuit law governs the validity and interpretation of such patent-specific local rules (at 1364), and wrote: “we see nothing in the Federal Rules that is inconsistent with local rules requiring the early disclosure of infringement and invalidity contentions and requiring amendments to contentions to be filed with diligence.” (At 1366.)

The court agreed “that ‘good cause’ requires a showing of diligence,” placed the burden on the party seeking to amend (at 1366), upheld a finding of a lack of diligence where O2 Micro waited almost three months after a deposition to serve proposed amendments, and affirmed summary judgment of noninfringement (at 1367, 1370).

Who answers for what a claim chart says?

The lawyer who signs it. Northern District Patent L.R. 2-3 requires all “statements, disclosures, or charts” filed or served under the rules to be dated and signed by counsel of record. The signature certifies that, to the best of counsel's knowledge, information and belief, “formed after an inquiry that is reasonable under the circumstances,” the information in the chart “is complete and correct at the time it is made.” The Eastern District of Texas's P.R. 2-3 uses the same certification.

The complaint is governed by Federal Rule of Civil Procedure 11(b): an attorney presenting a pleading certifies, after “an inquiry reasonable under the circumstances,” that “the factual contentions have evidentiary support” or, if so identified, will likely have it after discovery. Rule 11(d) states that the rule “does not apply to disclosures and discovery requests, responses, objections, and motions under Rules 26 through 37”; the local-rule certification, by its terms, reaches charts served under the patent rules.

What pre-suit investigation does Rule 11 require in a patent case?

At a minimum, a comparison of the claims with the accused product. In View Engineering, Inc. v. Robotic Vision Systems, Inc., 208 F.3d 981 (Fed. Cir. 2000), No. 99-1399, the court affirmed Rule 11 sanctions against a law firm over infringement counterclaims on eight patents. Judge Michel wrote that Rule 11 requires the firm, “at a bare minimum,” to “apply the claims of each and every patent that is being brought into the lawsuit to an accused device” and find a reasonable basis for infringement of at least one claim of each (at 986).

In Q-Pharma, Inc. v. Andrew Jergens Co., 360 F.3d 1295 (Fed. Cir. 2004), No. 03-1184, the court restated that Rule 11 requires “at a minimum, that an attorney interpret the asserted patent claims and compare the accused device with those claims before filing a claim alleging infringement” (at 1300 to 1301). It said “a claim chart is not a requirement of a pre-filing infringement analysis” (at 1301), and affirmed the denial of sanctions where the patentee had obtained a sample of the accused product, reviewed its advertising and labeling, and compared the claims with it (at 1302 to 1303).

What do court rules say about AI-drafted claim charts?

The rules covered here attach their obligations to the signature, not to the drafting method: Patent L.R. 2-3 applies to every chart counsel signs and Rule 11(b) to every pleading presented, with no exception for content produced with software. The Eastern District of Texas has addressed generative AI expressly. In General Order 25-07, signed on 31 October 2025, it amended Local Rule CV-11(g), effective 1 December 2025 subject to public notice and comment, so that all litigants remain responsible for the accuracy and quality of documents produced with generative AI.

The order's comment states: “The obligations of Fed. R. Civ. P. 11, and other similar legal and ethical requirements, apply regardless of how a filing is prepared.” Amended Local Rule AT-3(m) provides that a lawyer using such technology “continues to be bound by the requirements of Federal Rule of Civil Procedure 11” and must review and verify its output.

How can a claim chart be checked element by element?

Against the claim text and the cited evidence, row by row. The rules and decisions above suggest checks practitioners may consider for any chart, however drafted. Completeness: every limitation of every asserted claim has a row for every accused instrumentality, as Rule 3-1(c) requires, the claim language matches the issued claim, and, under Warner-Jenkinson, no row reads a limitation out of the claim through equivalents.

Evidence: each row cites where the limitation is found, such as a document page, a specification or a source-code location, and the cited material says what the row says. Each row also says how the cited feature meets the limitation, because the Northern District rule asks for both, and the Rule 2-3 certification is that the chart is “complete and correct.” Equivalents rows carry the Rule 3-1(e) explanation, and § 112(6) rows name the corresponding structure, act or material.

Consistency and a record: the rules, as O2 Micro put it quoting a district court, “require parties to crystallize their theories of the case early in the litigation” (at 1364), and a changed theory goes through Rule 3-6. A dated record of who compared which claims with which evidence bears on View Engineering's statement that a patentee, if challenged, must be prepared to show “exactly why” it believed before filing that it had a reasonable chance of proving infringement (at 986).