Expert Witnesses and Subpoena Duces Tecum

When an expert witness subpoena duces tecum is issued, it commands not oral testimony, but the production of tangible items. These may include records, documents, physical items such as defective products, or digital files used in expert testimony. Unlike a subpoena ad testificandum, which compels oral testimony, a subpoena duces tecum requires a person to produce documents or physical evidence under their possession or control.

This court order is frequently encountered in litigation involving expert witnesses, particularly when their report writing, file maintenance, or knowledge is critical to case outcomes.

When an Expert Witness Subpoena Duces Tecum May Be Issued

The issuance of a subpoena duces tecum is common in both civil and criminal litigation. In jurisdictions where depositions are permitted, counsel may serve this type of legal document on an expert in conjunction with a subpoena ad testificandum. This dual issuance obliges the expert witness not only to appear, but also to bring specific documents or deliver them in advance of their scheduled deposition.

Discovery practices differ by jurisdiction. In some states, records and other materials can be obtained by formal written request. In others, counsel must file a subpoena duces tecum to secure an expert’s files, particularly when those files contain critical physical evidence or analysis prepared in support of expert testimony.

Requirements for Disclosing Data and Documents

Under Rule 45 of the Federal Rules of Civil Procedure, parties responding to a subpoena duces tecum must produce documents in the condition they are ordinarily maintained. This includes electronic records, which must be presented in a format that is either routinely used or reasonably usable.

Information must be:

• Organized according to the categories specified in the subpoena
• Not deliberately disorganized or obscured to hinder review
• Fully disclosed unless valid grounds for withholding exist

An expert witness may not ignore or selectively withhold requested information—even if the materials might negatively impact the party retaining them. Any documents that are intentionally withheld must be identified, and opposing counsel must be notified of the omission.

Failure to comply with a valid subpoena duces tecum can expose the forensic expert to civil penalties or even criminal contempt. Attempts to circumvent disclosure through vague discussions or incomplete compliance are inadvisable and legally risky.

Exemptions and Limitations on Disclosure

Not all data must be turned over, even when requested. Rule 45 provides certain protections:

• Undue Burden or Cost: Electronic data that is not “reasonably accessible” due to excessive cost or technical challenges may be withheld. However, the resisting party must prove that the burden is excessive. Courts may still order discovery or issue protective orders to safeguard sensitive data.
• Privileged Information: Privileged communications are also exempt from disclosure. However, an expert witness should never unilaterally determine whether something is privileged. That decision must be made in consultation with the hiring attorney.

This is especially critical in criminal cases, where prosecutors are constitutionally bound under Brady v. Maryland, 373 U.S. 83 (1963), to disclose exculpatory evidence. Any expert working for the state must ensure full transparency with the prosecutor. If disputes arise over the interpretation of Brady, the expert may need to retain independent counsel to avoid personal liability.

Common Items Requested in a Subpoena Duces Tecum

While no two cases are identical, certain records are frequently demanded due to their evidentiary value. The following are standard items listed in many subpoena duces tecum demands:

• Complete expert witness file for the case
• All reports authored or reviewed by the expert
• Written or electronic communications regarding the case
• Notes, drafts, and preliminary analyses
• All data, assumptions, or facts provided by attorneys to the expert
• Professional background, including CV, licenses, and publications
• Scientific literature used to support conclusions
• Retainer agreements or contracts
• Time logs and billing records associated with the engagement

These materials are routinely used to assess the foundation of the expert’s testimony, evaluate credibility, and challenge conclusions during cross-examination.

Compensation for Compliance

Rule 45 also addresses payment for an expert’s time when complying with a subpoena duces tecum. The law mandates a “reasonable fee,” though this term remains undefined in statute. However, if compliance would impose manifest injustice—another legally ambiguous phrase—the requesting party may not be required to pay.

Experts should clarify their fee structure in advance and maintain detailed records of time spent fulfilling legal document requests. Failure to do so could delay or jeopardize payment for time spent responding to discovery demands.

What to Do If You Receive a Subpoena Duces Tecum

Receiving a subpoena duces tecum is not a matter to take lightly. It carries the same legal weight as a subpoena for oral testimony. Experts should treat such a court order with caution and professionalism. The first and most critical step is to contact the retaining attorney immediately. They can help assess the scope of the request, verify compliance obligations, and determine whether certain materials qualify for exemption or privilege.

Keep in mind that your reputation as an expert witness rests not only on the strength of your testimony, but also on your ability to comply fully with all legal obligations.