A non-retained expert witness subpoena is governed by Rule 45 of the Federal Rules of Civil Procedure, which starts from an unusual position: the court must quash the subpoena if it demands an unretained expert’s opinion or information drawn from study the expert conducted independently rather than at a party’s request.1Legal Information Institute. Federal Rules of Civil Procedure Rule 45 The requesting party can override that default only by meeting a demanding two-part test. If you’ve been served, or you’re trying to compel testimony from someone who has no connection to your case, the rules give both sides a defined path.
Who Counts as a Non-Retained Expert
A non-retained expert has no financial arrangement with any party and was not asked to study anything related to the case. Their involvement matters only because their independent work happens to touch on an issue in the litigation. Researchers, academics, and scientists whose published studies or datasets bear on a technical question are the typical examples. A geologist who published findings about groundwater contamination in a particular region might be pulled into a case about industrial pollution nearby.
This is different from a fact witness, who describes something they personally observed. A non-retained expert is valued for specialized knowledge, not eyewitness accounts. It is also different from a retained expert, who is hired and paid by a party to review case materials, form opinions, and testify.
The Default Protection Under Rule 45
Rule 45(a) allows a party or the party’s attorney to issue a subpoena commanding a person to attend and testify, produce documents and electronically stored information, or permit inspection of premises. The subpoena must issue from the court where the action is pending.
For non-retained experts, Rule 45(d)(3)(B)(ii) adds a protective layer that does not apply to ordinary witnesses. A court must quash or modify a subpoena if it demands disclosure of an unretained expert’s opinion or information that does not describe specific events in the dispute and comes from study the expert conducted independently.1Legal Information Institute. Federal Rules of Civil Procedure Rule 45 You cannot be forced to hand over your independent research or opinions just because they happen to be relevant to someone else’s lawsuit. The burden sits on the requesting party to justify overriding that default.
When a Court Will Override the Default
The protection is not absolute. Under Rule 45(d)(3)(C), a court may allow the subpoena to proceed if the requesting party meets two conditions. First, they must show a substantial need for the testimony or material that cannot be met without undue hardship. Second, they must ensure the subpoenaed expert will be reasonably compensated.1Legal Information Institute. Federal Rules of Civil Procedure Rule 45 Both must be satisfied. Showing need without offering compensation is not enough.
The substantial need test is genuinely difficult to satisfy. Courts ask whether the party could hire their own expert to perform the same analysis. If yes, compelling an uninvolved professional is hard to justify. The requesting party typically must show that the non-retained expert possesses a unique dataset, methodology, or set of findings that cannot be replicated. A researcher who is the only person to have studied a particular site, population, or phenomenon before it changed is the classic example.
Courts also draw a line between asking an expert to describe work they have already completed and asking them to generate new analysis. A subpoena can require you to explain the methodology behind a published paper or confirm data you already collected. It cannot conscript you into performing fresh analysis on case-specific facts. Courts consistently reject that second use.
Geographic Limits on Where You Can Be Compelled
Rule 45(c)(1) restricts where a subpoena can compel attendance for a trial, hearing, or deposition. Generally, a non-party witness can be required to appear only within 100 miles of where they reside, work, or regularly conduct business in person.1Legal Information Institute. Federal Rules of Civil Procedure Rule 45
A narrow exception exists for trials: a witness can be commanded to attend a trial anywhere within the state where they reside, work, or regularly transact business, provided they would not incur substantial expense. The exception does not apply to depositions. A researcher in Boston cannot be forced to sit for a deposition in Los Angeles simply because the case is pending there. The requesting party would need to arrange the deposition closer to the expert or use remote means if the expert consents.
How to Respond to the Subpoena
Doing nothing is not an option. The rules give you specific tools, and using them within the deadlines matters.
Written Objections
When a subpoena commands you to produce documents or tangible items, you may serve written objections on the party who issued it. The deadline is the earlier of the date specified for compliance or 14 days after you receive the subpoena.1Legal Information Institute. Federal Rules of Civil Procedure Rule 45 Missing this window can waive your objections.
Motion to Quash or Modify
You can also file a formal motion asking the court to quash the subpoena entirely or modify it to reduce the burden. Non-retained experts start from a favorable position because Rule 45(d)(3)(B)(ii) creates a presumption in favor of quashing.1Legal Information Institute. Federal Rules of Civil Procedure Rule 45 The party who issued the subpoena then bears the burden of showing substantial need and offering reasonable compensation.
Judges weigh several factors when deciding these motions. They consider how relevant the expert’s knowledge is compared to the intrusion on the expert’s time and career. A subpoena that sweeps in everything an expert has ever worked on is almost certainly going to be narrowed or quashed. One targeting a specific published dataset or defined set of findings stands a better chance of surviving. Courts also look at whether the expert’s ongoing research or professional obligations would be disrupted. Participation that would set back a multi-year study or force disclosure of unpublished work in progress weighs heavily in the expert’s favor.
Negotiating First
Before filing a motion, try to negotiate with the requesting party. Offering a subset of data or a limited scope of testimony often resolves the issue without court intervention. Judges look favorably on these good-faith efforts and are more likely to impose protective conditions when a party refused reasonable accommodations.
Protecting Confidential Research and Unpublished Work
Rule 45(d)(3)(B) separately recognizes trade secrets and confidential research as grounds for quashing or modifying a subpoena. If a subpoena would require disclosure of trade secrets or other confidential research, development, or commercial information, the court must quash or modify it unless the requesting party meets the substantial need standard.1Legal Information Institute. Federal Rules of Civil Procedure Rule 45
Even when a court decides the subpoena should go forward, it can issue a protective order under Rule 26(c) to limit how the information is used.2Legal Information Institute. Federal Rules of Civil Procedure Rule 26 – Duty to Disclose General Provisions Governing Discovery Typical provisions restrict access to attorneys and experts working on the case, prohibit use of the data outside the litigation, and require that all materials be returned or destroyed when the case concludes. Violations can result in contempt sanctions.
Certain federally funded research may qualify for additional protection under confidentiality certificates that shield the identity of research subjects from disclosure in legal proceedings. If your research involves human subjects and is federally supported, checking whether you have or can obtain a confidentiality certificate is worth doing before responding to any subpoena.
Compensation You Are Entitled To
Serving a subpoena requires tendering fees for one day’s attendance and the mileage allowed by law.1Legal Information Institute. Federal Rules of Civil Procedure Rule 45 In federal court the statutory attendance fee is $40 per day, plus a mileage allowance pegged to the rate the General Services Administration sets for federal employees.3Office of the Law Revision Counsel. 28 USC 1821 – Per Diem and Mileage Generally This is a floor, not a ceiling.
When a court permits a non-retained expert subpoena to proceed, Rule 45(d)(3)(C) requires the requesting party to ensure “reasonable compensation,” which means payment well above the statutory witness fee.1Legal Information Institute. Federal Rules of Civil Procedure Rule 45 Rule 26(b)(4)(E) separately requires the party seeking discovery from an expert to pay a reasonable fee for the expert’s time spent responding, unless that would result in manifest injustice.2Legal Information Institute. Federal Rules of Civil Procedure Rule 26 – Duty to Disclose General Provisions Governing Discovery
What counts as reasonable depends on the field, credentials, and going rate for comparable professionals. Hourly rates commonly fall between $200 and $1,000 or more, with medical specialists, forensic accountants, and technology experts at the higher end. Courts have discretion to set different rates for different activities. One federal court approved $500 per hour for deposition testimony but reduced the rate to $350 per hour for preparation time, reasoning that preparation is less demanding than live questioning.4United States District Court for the District of Kansas. Memorandum and Order Case No 05-2093-JWL-DJW Reasonable compensation also covers preparation time and travel expenses, not just time spent answering questions.
A Note on Treating Physicians
Treating physicians are often lumped into this category, but they occupy a middle ground. A doctor who treated a plaintiff’s injuries was not hired as an expert, yet their firsthand knowledge of the patient’s condition carries significant weight. Federal courts generally classify treating physicians as non-retained experts under Rule 26(a)(2)(C), with lighter disclosure obligations than a retained expert but heavier ones than an ordinary fact witness.2Legal Information Institute. Federal Rules of Civil Procedure Rule 26 – Duty to Disclose General Provisions Governing Discovery
Scope is where disputes arise. Most courts allow physicians to testify about what they observed and concluded during treatment without preparing a full expert report. Diagnosis, treatment decisions, and clinical observations typically fall within that scope. Testimony about causation, long-term prognosis, or impairment ratings is contested, and federal courts are divided on whether those opinions can come from treatment alone or whether they require a formal written report under Rule 26(a)(2)(B). Reviewing additional records provided by an attorney or formulating opinions about issues the physician did not address during treatment can push them into retained-expert territory with far more demanding disclosure requirements.
Disclosure Obligations If You Testify
When a party plans to call a non-retained expert at trial, they must provide the opposing side with a disclosure under Rule 26(a)(2)(C). This disclosure requires only two things: the subject matter on which the witness will present testimony, and a summary of the facts and opinions the witness is expected to offer.2Legal Information Institute. Federal Rules of Civil Procedure Rule 26 – Duty to Disclose General Provisions Governing Discovery That is far lighter than the signed written report retained experts must produce.
One trap: the summary must be substantive. Directing the other side to “see the medical records” or “see the published study” is not enough. The party calling the non-retained expert must actually describe the facts and opinions the witness will cover, even if briefly.
What Happens If You Ignore the Subpoena
Simply ignoring a subpoena is never a safe response, even if you believe it is overbroad or unjustified. Under Rule 45(g), any person who has been properly served and fails without adequate excuse to obey a subpoena can be held in contempt of court.1Legal Information Institute. Federal Rules of Civil Procedure Rule 45 Civil contempt is the most common tool. It is designed to coerce compliance, meaning sanctions continue until you comply, including daily fines that accumulate until you appear or produce what was requested.
Rule 37 also allows courts to order the non-compliant person or their attorney to pay the reasonable expenses the requesting party incurred because of the failure to comply, including attorney’s fees.5Legal Information Institute. Federal Rules of Civil Procedure Rule 37 – Failure to Make Disclosures or to Cooperate in Discovery Sanctions Courts will not impose costs if the failure was substantially justified or if other circumstances make an award unjust, but that is a narrow escape hatch. If you have legitimate grounds to resist, use the written objection and motion to quash. Do not simply fail to show up.