Can A Non-Retained Expert Be Compelled To Testify?

Christine Funk

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— Updated on September 1, 2021

Can A Non-Retained Expert Be Compelled To Testify?



When neither side actually retains a named expert, the courts rarely require non-retained witnesses to testify.  However, it can happen in certain, rare circumstances.   When the issue does present itself, the Rules of Civil Procedure, along with caselaw, provide a roadmap for litigants and the court to determine whether to force testimony.

Differences Between Expert and Non-Retained Witnesses

Non-retained witnesses can be compelled to testify, in part, as they are merely relaying what they saw, what they heard, or what they otherwise witnessed.  They are important by virtue of where they were in relation to the event subject to litigation as well as their unique knowledge of what transpired.  Expert witnesses, on the other hand, testify about what they know based on their professional efforts in a given field.

Differing Requirements for Expert and Non-Retained Witnesses

While non-retained witnesses require some disclosure, expert witnesses require far more.  It may be challenging to compel an expert witness to testify, in part, because before an expert witness is deposed or testifies, the federal rules require the disclosure of a report.  Federal Rule of Civil Procedure 26 (a) (2) (B) calls for the disclosure of a report including:

  1. A complete statement of all the opinions a witness plans to express, as well as the basis for the opinions, and the reasons supporting the opinions
  2. The facts or data relied on or considered when forming the opinion
  3. Exhibits the expert will use to support or summarize their findings
  4. Their qualifications and the last 10 years of their publications
  5. All other cases the witness testified as an expert, whether in trial or deposition
  6. A statement of compensation the expert has been or will be paid for the study and testimony in the case at hand

Obviously, it will be difficult, if not impossible, to obtain this information in a report from a non-compensated, unretained expert.

Challenges to Subpoenas

Simply serving a subpoena on an expert witness, with the expectation they then make themselves available for deposition or trial testimony, will inevitably result in objections from the jury.  Objections may include the following:

  1. Testimony about an expert’s findings may impact or limit an expert’s ability to conduct research
  2. Testimony about an expert’s work may be unethical, if the work is not completed, peer reviewed, or otherwise in a “publishable” format
  3. The subpoena and resultant testimony could put the expert at a competitive disadvantage
  4. Work required to adequately prepare for such testimony is overly burdensome
  5. The subpoena and subsequent testimony may put the unwilling expert in a controversial or otherwise uncomfortable position

The Rules of Civil Procedure specifically allow for quashing a subpoena in certain cases, including to protect a person subject to or affected by a subpoena, who is an expert.  Rule 45 (d) (3) (B) (ii) provides a court may, on motion, “quash or modify the subpoena if it requires disclosing an unretained expert’s opinion or information that does not describe specific occurrences in dispute and results from the expert’s study not requested by a party.”

Basis for Seeking Non-Retained Experts

Recently, in In Re: World Trade Center Lower Manhattan Disaster Site Litigation, United States District Court, D.D. New York, (January 15, 2015), the court addressed the issue of calling non-retained experts.  In World Trade Center, the injured plaintiffs sought the introduction of the testimony of non-retained experts in support of their claim the injuries they incurred were the result of breathing or ingesting the dust from the collapsed Twin Towers of the World Trade Center.  The non-retained experts included physicians associated with the Mount Sinai World Trade Center Medical Monitoring Program (Mt. Sinai WTC Health Program), along with one other treating physician.  They argued these non-retained experts had unique knowledge of the effects of the dust from the World Trade Center collapse.  However, the identified experts were not willing to serve as expert witnesses on behalf of the plaintiff, nor provide data they had gathered.

Mount Sinai refused to allow their physicians to participate or cooperate with the plaintiffs.  Mount Sinai indicated they were concerned about the amount of time cooperation would take, as this would limit the amount of time the experts would have for ongoing research and continuing to see patients.  Further, they argued testifying for the plaintiffs would compromise the institution’s position of neutrality in the World Trade Center litigation.  The additional treating physician also argued there would be a conflict of interest with his other employment, were he to testify for the plaintiffs.

Dealing with the Reporting Requirements

Because the non-retained experts wouldn’t complete reports required by Rule 26, the plaintiffs provided abbreviated expert disclosures.  These reports consisted of generic summaries of the experts’ anticipated opinions.  When the court held these reports did not comply with the rules, the plaintiffs filed a motion to compel the experts to provide the required reports.

The Powers of the Court

The court found they have the power to compel a non-retained expert to either produce documents or provide testimony, noting it is within their “sound discretion” pursuant to Federal Rule of Civil Procedure 45 (d) (3) (C).  This is permissible assuming two requirements are met.  First, the witness will be reasonably compensated.  Second, the parties show a “substantial need for the testimony or material that cannot be otherwise met without undue hardship.”  World Trade Center, citing, Fed. R. Civ. Pro. 45 and Carter-Wallace, Inc. v. Otte, 474 F.2d 529, 536 (2d Cir. 1972).  It is important to note, this testimony is limited to requiring witnesses to testify to opinions previously formed.  It does not expand to require witnesses to review data in specific cases to formulate new opinions.

The Five Factors

There are five factors courts consider when determining whether to use their discretion to force testimony.  These factors are:

  1. The degree to which an expert is being called based on relevant facts of the case as opposed to providing opinion testimony
  2. The difference between forming a new opinion as opposed to testifying about a previously formed opinion
  3. Whether the witness is a unique expert for reasons other than their expert status;
  4. The extent to which a party can show there is unlikely any comparable witness who is willing and available to provide testimony
  5. The degree a proposed witness shows oppression by courts constantly or continually compelling testimony about their knowledge

Kaufman v. Edelstein, 539 F.2d 811, 822 (2d Cir. 1976).

The Decision

The court engaged in an analysis, weighing the merits for and against compelling deposition and trial testimony of the experts.  After careful consideration, the court found the plaintiffs had not demonstrated a substantial need for the testimony which “cannot be otherwise met without undue hardship” pursuant to Rule 45 of the Federal Rules of Civil Procedure.  However, the court found the research data accumulated by the Mount Sinai WTC Health Program was “unparalleled in its scope.”  Consequently, the court ordered disclosure of the data.


At the end of the day, the circumstances under which a judge forces a non-retained expert to testify are rare.  When this occurs, the court does not compel the review of facts and circumstances of a given case, with the expectation the expert provide specific testimony about a specific injury or lack thereof.  Rather, the witness only provides information on opinions previously held.

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