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Expert Witness Disclosure: The Who, What, When, and How of Avoiding Exclusion

Dani Alexis Ryskamp, J.D.

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— Updated on April 27, 2022

Expert Witness Disclosure: The Who, What, When, and How of Avoiding Exclusion


Both expert witnesses and the attorneys who retain them focus early on establishing the expert’s credentials, analytical approach, and opinions in order to survive a Daubert challenge or to persuade a jury. Before either of these steps occur, however, the witness’s expert status must be disclosed. Attending closely to the details at this stage minimizes the risk that an expert witness’s opinions will be excluded from testimony – or that the witness will be dismissed altogether.

Who Is an Expert?

Federal Rules of Evidence 702, 703, and 705 require parties to disclose any witnesses they may use at trial. Additionally, Federal Rule of Evidence 701 distinguishes between expert and lay testimony – but it does not distinguish between expert and lay witnesses.

What’s the difference? Simply speaking, while both lay and expert testimony may encompass facts, only the latter may also include opinions reasoned from those facts. Rule 701 provides that lay testimony may not “provide specialized explanations or interpretations that an untrained lay person could not make if perceiving the same acts or events.” Such opinions given by a lay witness (one not disclosed or accepted as an expert) will likely be prohibited or excluded from the record.

Because the boundary between “untrained” and “expert” opinions is not always clear, one strategy is to identify any witness who might need to give an opinion as an “expert witness.” In some cases, the “expert” may be a client or a client’s employee, who can discuss not only the “what” of the case but also the “what it means” in context.

When is Disclosure Necessary?

Reporting requirements for experts are articulated in Federal Rule of Civil Procedure 26(a)(2)(B), which states that an expert must submit a written disclosure report when:

  1. The expert was “retained or specially employed to provide expert testimony,” or
  2. The expert’s “duties as the party’s employee regularly involve giving expert testimony.”

Not all experts may be required to submit a report under FRCP 26(a)(2)(B). An expert whose opinions are based on firsthand knowledge, and who does not regularly serve as an expert, may not be required to submit a report. For instance, a treating physician who testifies as to her firsthand knowledge gained from treating a patient may not be required to submit a report, because the physician is not considered “retained or specially employed” to provide testimony about her own evaluation and treatment. A physician who was hired to review the case secondhand and provide an opinion, however, would be required to submit a report.

Like the question “Who is an expert witness?”, the question “Does this expert need to submit a report?” is not always clear, particularly in the case of employee experts. One way to address the lack of clarity is to submit a report for every expert, whether or not it is required.

What Information Must Be Disclosed?

FRCP 26(a)(2)(B) specifies not only who must submit a written disclosure report, but also what the report must contain. The report must include “a complete statement of all opinions the witness will express and the basis and reasons for them.” It must also include:

  1. The expert’s qualifications,
  2. The data or other information the expert considered in order to form an opinion,
  3. A complete list of the expert’s publications in the past ten years,
  4. A complete list of cases in which the expert testified (at deposition or trial) in the previous four years,
  5. The compensation paid to the expert,
  6. Any necessary supporting exhibits.

In creating a report, attention must be paid to completeness and detail. A complete report should indicate the substance of direct examination, and it should demonstrate that the witness’s testimony is admissible without requiring the court to inquire further.

How Does Disclosure Occur?

Ideally, an expert witness will write his or her own report; however, in practice, many attorneys find that they need to provide guidance on formatting and content in order to ensure the resulting report meets procedural requirements.

While attorneys may assist expert witnesses in preparing the written report, the final product should accurately reflect the witness’s credentials and experience, and it should be signed by the witness. Courts have varied on how much attorney assistance they will permit, but they generally agree that counsel may not draft the entire written disclosure without the expert’s input.

FRCP 26(a)(2)(B) requires that reports be submitted 90 days before trial and that rebuttals be submitted 30 days after the other party’s disclosure. However, a stipulation or a specific date set by the court can (and often does) change this deadline in specific cases.

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