Interrogatories in U.S. Litigation

Interrogatories are written questions that one party in a civil lawsuit formally poses to another party, who must respond in writing under oath. This page covers the definition, procedural mechanics, typical use cases, and strategic boundaries of interrogatories within U.S. federal and state litigation. As a tool within the broader discovery process in U.S. litigation, interrogatories occupy a defined role alongside depositions, document requests, and admissions — each with distinct limits and purposes.

Definition and scope

Interrogatories are a formal discovery device governed at the federal level by Rule 33 of the Federal Rules of Civil Procedure (FRCP). Under FRCP Rule 33(a)(1), a party may serve no more than 25 written interrogatories on any other party, including all discrete subparts, unless the court orders or the parties stipulate to a different number. State court systems impose their own limits — California's Code of Civil Procedure § 2030.030, for example, caps interrogatories at 35 specially prepared questions for most cases, in addition to a separate set of Judicial Council form interrogatories.

Interrogatories may only be directed at parties to the litigation, distinguishing them from subpoenas, which can compel responses from non-parties. The responding party must answer each question separately and fully, or state an objection with specificity, within 30 days of service under FRCP Rule 33(b)(2) — a period that may be modified by agreement or court order.

Two primary categories of interrogatories exist in practice:

The federal rules of civil procedure page details how Rule 33 fits within the full FRCP discovery framework.

How it works

The interrogatory process follows a structured sequence tied to the case scheduling order and overall discovery timeline:

  1. Service: The propounding party drafts and serves interrogatories on the opposing party. Under FRCP Rule 26(d), interrogatories generally cannot be served before the parties have conducted their Rule 26(f) conference, unless stipulated or court-ordered.
  2. Review and objection deadline: The responding party has 30 days (FRCP Rule 33(b)(2)) to serve written responses. Extensions are commonly granted by stipulation but require court approval if they push past scheduling deadlines.
  3. Response format: Each interrogatory receives a separate written answer, signed under oath by the party (not counsel). Objections must state the grounds with specificity; boilerplate objections such as "overbroad and unduly burdensome" without further explanation risk being overruled or sanctioned.
  4. Business record option: FRCP Rule 33(d) permits a party to respond by specifying business records from which the answer can be derived, provided the burden of finding the answer is substantially the same for both parties. This provision is frequently invoked in complex commercial cases involving large document volumes.
  5. Meet and confer: If responses are deficient, the propounding party must attempt to resolve the dispute informally before filing a motion to compel, per FRCP Rule 37(a)(1). Courts routinely deny motions to compel that lack a good-faith meet-and-confer certification.
  6. Motion to compel or for protective order: Unresolved disputes proceed by motion. The court may compel further responses, issue a protective order, or impose sanctions in U.S. litigation for willful non-compliance.

Answers to interrogatories are signed under penalty of perjury, making them admissible at trial as party admissions under Federal Rule of Evidence 801(d)(2).

Common scenarios

Interrogatories are deployed across civil litigation contexts, with usage patterns varying by case type:

Commercial disputes: Parties use interrogatories to identify all individuals with knowledge of a breach, pin down the timeline of contract performance, and establish the factual basis for damages calculations before depositions.

Personal injury and tort cases: Plaintiffs typically serve interrogatories seeking the identity of all witnesses, a description of the incident, insurance coverage details, and prior similar incidents. Defendants use interrogatories to probe the plaintiff's medical history, employment record, and prior litigation history.

Employment litigation: Interrogatories are used to identify comparator employees, document the defendant's anti-discrimination policies, and establish the timeline of adverse employment actions. California's Judicial Council Employment Law form interrogatories (DISC-001 series) are frequently used in state court proceedings.

Class action litigation: In class action litigation in U.S. courts, interrogatories at the class certification stage often focus on numerosity data, common questions of law and fact, and the defendant's policies applied uniformly across the putative class.

Electronic discovery interface: Interrogatories frequently accompany electronic discovery (eDiscovery) requests, asking parties to identify custodians, describe data retention systems, and confirm the scope of litigation holds issued under litigation holds and document preservation obligations.

Interrogatories serve a foundational role in narrowing issues before depositions. Identifying key witnesses and document custodians through interrogatory answers allows counsel to target deposition questioning more efficiently.

Decision boundaries

Interrogatories are not universally the right tool, and their limits define when other discovery mechanisms apply instead.

Interrogatories vs. depositions: Interrogatories elicit party-controlled, counsel-reviewed answers prepared over 30 days. Depositions in U.S. litigation capture spontaneous oral testimony that cannot be sanitized through attorney review before the answer is given. For testing credibility or probing evasive witnesses, depositions are more effective. For establishing undisputed background facts, interrogatories are more efficient.

Interrogatories vs. requests for admission: Requests for admission are designed to eliminate genuinely undisputed facts from trial. Interrogatories are designed to obtain information, not conclusively establish facts. A party may deny an interrogatory answer at trial; a properly admitted request for admission is binding.

Interrogatories vs. requests for production: Requests for production compel the disclosure of documents, electronically stored information, and tangible things. Interrogatories elicit narrative explanations and identifications. The two tools are routinely served simultaneously, with interrogatories asking parties to identify documents and production requests compelling their delivery.

Numerical ceiling as a strategic constraint: The 25-interrogatory federal cap under FRCP Rule 33(a)(1) forces prioritization. Courts generally deny leave to exceed the limit absent a demonstrated showing that the case's complexity requires it. Parties in multidistrict litigation proceedings (multidistrict litigation (MDL)) may negotiate coordinated interrogatory protocols across consolidated cases.

Scope of permissible content: Interrogatories are subject to the same relevance and proportionality standards that govern all discovery under FRCP Rule 26(b)(1). Proportionality analysis weighs the importance of the information, the parties' relative access to it, the parties' resources, and the burden or expense of responding. Courts applying this standard have denied interrogatories seeking information whose marginal value does not justify the production burden.

Privilege and work product: Answers may be withheld on grounds of attorney-client privilege in litigation or the work product doctrine, but the withholding party must serve a privilege log identifying each withheld item with sufficient detail for the court to assess the claim.

References

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