Expert Witness Discovery Rules: Consulting vs. Testifying Experts


Expert Witness Discovery Rules

Depending on the jurisdiction and the nature of the case, the methods employed for the discovery of expert witnesses may include interrogatories, depositions, informal meetings, phone calls, or email exchanges. But before you get to discovery, you must determine whether your expert’s identity needs to be disclosed and — if you choose to disclose your expert — what areas of inquiry are legally supportable and what topics are off limits.

Do You Need to Disclose Your Expert Witness?

As a preliminary matter, check the rules, check the rules, check the rules. While most states conform to the federal rules, not all of them do. Some states have different rules, so it is a good idea to review the rules regarding disclosure in your jurisdiction before proceeding. Additionally, expert witness disclosure varies based on whether you are handling a civil case or a criminal case. In criminal cases, your disclosure obligations also vary based on whether you are the prosecutor or the defense attorney. Generally speaking, Brady v. Maryland, 373 U.S. 83 (1963) requires prosecutors disclose the identity and opinion of an expert witness who provides information which tends to exculpate the defendant or mitigate their conduct. As such, a criminal prosecutor has a different ethical obligation than criminal defense attorneys as well as civil litigants.

Disclosing the Identity and Opinions of Testifying Experts

Rule 26 (a) (2) of the Federal Rules of Civil Procedure calls for the disclosure of any expert witness “it may use at trial to present evidence under Federal Rule of Evidence 702, 703, or 705.”[1] In other words, Rule 26 (a) (2) addresses what must be done with testifying experts and upholds that their identities must be disclosed.

In addition to disclosing an expert witness’s identity, the Federal Rules call for additional disclosures. Unless there are other orders by the court or stipulations to the contrary, when disclosing an expert witness, the party must also disclose a report, prepared and signed by the witness. The report must include the following information:

  1. All opinions the witness will testify to, as well as the basis and reasons for the opinions held.
  2. The data or facts the witness considered when forming their opinion.
  3. Disclosure of any exhibits the expert witness intends to use to summarize or support his or her opinions.
  4. The qualifications of the witness, including a list of all publications the expert witness has authored in the past ten years.
  5. A list of cases the expert witness provided deposition testimony or trial testimony during the past four years.
  6. A statement regarding the expert witness’s compensation for the review and evaluation of the evidence, as well as their testimony in the case.

Federal Rule of Civil Procedure 26 (a) (2) (B) (i – vi). Typically, the Federal Rules call for disclosure at least 90 days before the trial date for expert witnesses called in one’s case in chief. For rebuttal witnesses, or rebuttal testimony obtained after receipt and review of the original expert’s reports, the disclosure must take place within 30 days of the other side’s disclosure, pursuant to Rule 26 (a) (2) (D) (i, ii). Additions or changes to an expert’s report must be disclosed at the time the pretrial disclosures are due.

Drafts of the report are protected. Additionally, communications between the expert witness and the attorney who hired the expert are protected. The exception to the protection on communications encompass those areas subject to disclosure in the expert reports, namely:

  1. Communications related to compensation for case evaluation and testimony.
  2. The facts or data an attorney provides the expert witness, which the expert considered in forming their opinions.
  3. The assumptions provided by the attorney which the expert witness relied upon when forming their opinion.

Once the expert witnesses have disclosed their written reports, the parties may depose the experts.

Disclosing the Identity and Opinions of Non-Testifying Experts

When it comes to disclosing the opinions of non-testifying experts, the Federal Rules are clear. Rule 26 (B) (4) (D) recognizes that ordinarily, facts and opinions known or held by experts who are either retained in anticipation of litigation or for trial preparation assistance and not expected to be called as a witness generally are not subject to interrogatories or depositions. There is an exception for when the other side makes a showing of “exceptional circumstances under which it is impracticable for the party to obtain facts or opinions on the same subject by other means.” Rule 26 (B) (4) (D) (ii).

Whether one must disclose the identity of non-testifying experts varies depending on jurisdiction. For example, in Baki v. B.F. Diamond Construction, 71 F.R.D. 179 (D. Md. 1976), the United States District Court for the District of Maryland held Federal Rule of Civil Procedure Rule 26 (b) (1), now codified as (a) (1) (A), which states the parties must disclose “the name, . . . the address and telephone number of each individual likely to have discoverable information. . .” includes a mandate parties must disclose the name of consulting experts, even if they don’t plan to call them as testifying witnesses at trial.

On the other hand, in Ager v. Jane C. Stormont Hospital and Training School for Nurses, 622 F.2d 496 (10th Cir. 1980), the United States Court of Appeals for the Tenth Circuit held the opposite. Under their reasoning, in order to compel discovery of a non-witness expert, the other side must show “exceptional circumstances under which it is impracticable for the party seeking discovery to obtain facts or opinions on the same subject by other means.”

In Conclusion

Introducing expert witness testimony is the culmination of hours of careful preparation and evaluation. Lawyers must understand their discovery obligations, whether in criminal or civil cases, whether in state or federal court. Taking the time to determine the relevant rule, as well as whether the expert will testify or merely consult, is critical to success.


[1] Federal Rule of Evidence 702 deals directly with testimony by expert witnesses; 703 covers the bases of an expert’s opinion; and 705 addresses the disclosure of facts or data underlying an expert’s opinion, and the elicitation of that evidence on direct or cross examination.

About The Author

Christine Funk, J.D., is a dual-qualified criminal defense attorney and forensic science consultant who has trained lawyers, judges, and law enforcement across three continents in various forensic science disciplines.

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