The Rule 26(a)(2)(B) expert report: a plain-English completeness checklist

Federal Rule of Civil Procedure 26(a)(2)(B) lists six things a retained expert's written report must contain. They are not aspirational. They are the floor. When a report is missing one of them, or addresses it too thinly, opposing counsel has a ready motion. Under Rule 37(c)(1), a party that fails to make the required disclosure is presumptively barred from using that information or witness at trial or on a motion, unless the failure was substantially justified or harmless. The burden of showing justification or harmlessness falls on the party offering the expert, not on the party objecting.

The six elements are well settled. What varies, and what actually gets reports struck or testimony limited, is whether each element is addressed with enough specificity. This checklist works through each one in plain English: what the rule calls for, and what reviewers and opposing counsel look for when they read the report.

The six required elements

(i) A complete statement of all opinions and the basis and reasons for them

This is the core of the report. The rule requires not just the conclusion but the reasoning path: why this opinion, grounded in what. “Complete” is doing real work in that phrase. Courts have excluded supplemental opinions offered at trial when they were not in the original report, even if the expert could have formed them earlier. Here is the practical test. If an opinion the expert intends to give at trial isn't in the report with its basis and reasons, it is at risk.

Opposing counsel will look for opinions stated as conclusions without the underlying reasoning, and for opinions that seem to have appeared after the disclosure deadline. Both invite a motion to exclude or limit.

(ii) The facts or data the expert considered

The report must disclose what the expert actually reviewed and relied on. Not a general description of the type of materials an expert in this field typically considers, but the specific records, data sets, studies, and other materials this expert looked at in forming these opinions. If a document was reviewed, it belongs in the list. If the expert considered it and set it aside, that too is within the scope of “considered.”

The consequence of incompleteness here is exposure on cross: opposing counsel can challenge an opinion by showing the expert considered materials not listed (suggesting something was concealed) or failed to consider materials that were available (suggesting the opinion is incomplete). The list is the chain of custody for the expert's reasoning.

(iii) Any exhibits used to summarize or support the opinions

Exhibits that will be used at trial to summarize or support the opinions must be identified in the report. This includes charts, tables, timelines, photographs, and any other visual or documentary aids the expert intends to use. The purpose of this requirement is to give opposing counsel a fair opportunity to examine and challenge the supporting materials before trial, not to encounter them for the first time at the witness stand.

Exhibits identified in the report are not automatically admitted; they still need to clear the usual evidentiary thresholds. But exhibits the expert plans to use that are absent from the report are a straightforward target for exclusion.

(iv) The witness's qualifications, including all publications in the previous 10 years

The qualifications section must include a list of the witness's publications from the previous ten years. A curriculum vitae attached to the report generally satisfies this, but only if the CV itself contains that information accurately. An incomplete or outdated CV creates a credibility problem that opposing counsel will find, whether it omits publications, misstates dates, or lists credentials that have lapsed.

Relevant qualifications for the opinions at issue should be legible in the report itself, not just attached as a background document. A judge ruling on a Daubert challenge, or a jury evaluating the expert, benefits from understanding why this person is qualified to offer these specific opinions.

(v) A list of all other cases in which the witness testified in the previous 4 years

The report must include a list of every case in which the expert testified (at trial or by deposition) during the previous four years. The list should identify the case by name, court, and docket number where available, and note whether the testimony was at trial or deposition. This section exists to allow opposing counsel to locate and review prior testimony, looking for inconsistencies between what the expert has said in other matters and what the expert is saying now.

A thin or missing prior-testimony section is one of the most commonly flagged incompleteness issues. An expert who testifies regularly and produces a list of only a handful of cases will face questions about what was left off. This section should be thorough and current to the report date.

(vi) A statement of the compensation to be paid

The report must state the compensation the expert is being paid for the study and testimony. This requirement exists because an expert's financial relationship with the retaining party is fair game on cross-examination. It bears on potential bias. The statement should cover the expert's rate and, where the arrangement is relevant, whether compensation depends on the outcome of the litigation (which it generally should not).

This element is brief, but its absence is noticed. Opposing counsel reviewing a report for Rule 26 completeness will check for it, and a missing compensation statement is an easy motion.

Where reports actually fall short

The six elements are well known to experienced expert witnesses. The gaps that generate motions tend to fall into a smaller set of recurring patterns.

• Opinions stated without the basis shown. The expert gives the conclusion (a range, a finding, a determination), but the report does not walk through the reasoning that produced it. This is the element (i) failure mode, and it is the one most likely to support a Daubert exclusion on top of a Rule 26 objection.
• Materials considered but not disclosed. An expert reviews a document, forms a view of it, and the document does not appear in the element (ii) list. Whether or not the expert relied on it in the final opinion, it was considered. And the rule requires disclosure of what was considered, not just what was ultimately cited.
• A thin or missing prior-testimony section. The element (v) list covers four years of trial and deposition testimony, across all cases. Experts who testify regularly often underestimate how long that list should be, or omit cases they view as minor or unrelated.
• Supplementation handled late. Rule 26(e) requires a party to supplement or correct an expert disclosure in a timely manner. When new information emerges or the expert forms additional opinions, supplementation that comes close to or after the discovery cutoff can be challenged as untimely. And untimely supplements often do not cure the original deficiency for purposes of Rule 37(c)(1).

Completeness and Rule 702: what they do and don't do for each other

Rule 26(a)(2)(B) governs what a report must contain. Federal Rule of Evidence 702, as amended effective December 1, 2023, governs whether the opinion is reliable enough to reach the jury. They operate at different stages (Rule 26 at disclosure, Rule 702 at the admissibility hearing), but they are related in a practical way.

The 2023 amendments to Rule 702 made explicit what courts had long applied: the opinion must rest on sufficient facts or data and reflect a reliable application of reliable methods, and the burden is on the party offering the expert to establish those requirements by a preponderance of the evidence. The court, not the jury, decides whether the expert clears the threshold. Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), and the cases that followed it, are the framework courts use to apply that reliability screen.

A complete Rule 26 report supports reliability by making the methodology visible: the data that was considered, the reasoning path from that data to the opinion, the expert's qualifications to apply the method. Completeness does not guarantee that the opinion will survive a Daubert challenge; that depends on the underlying methodology. But incompleteness makes a Daubert challenge easier: a report that conceals or omits the basis for an opinion gives the court less to evaluate, and the burden is on the proponent. Completeness is not sufficient for admissibility, but incompleteness is often sufficient for exclusion.

Sources

• Fed. R. Civ. P. 26(a)(2)(B).
• Fed. R. Civ. P. 37(c)(1).
• Fed. R. Evid. 702 (as amended Dec. 1, 2023).
• Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993).

General information, not legal advice. Disclosed. is a software company, not a law firm. This article describes federal procedural rules in general terms; rules vary by jurisdiction and local rule, and courts interpret and apply them differently. Verify all requirements against the official rules and any applicable local rules, and consult counsel about your own matter before relying on anything here.