Rule 213.Written Interrogatories to Parties
Article II. Rules on Civil Proceedings in the Trial Court · Part E. Discovery, Requests for Admission, and Pretrial Procedure · Last amended 2018 · Last verified July 20, 2026
In one sentenceRule 213 is Illinois's interrogatory rule — capping the number of questions, setting a 28-day answer deadline, and requiring detailed disclosure of trial witnesses depending on what kind of witness they are.
Full Text of Ill. S. Ct. R. 213
(a) Directing Interrogatories. A party may direct written interrogatories to any other party.
A copy of the interrogatories shall be served on all other parties entitled to notice.
(b) Duty of Attorney. It is the duty of an attorney directing interrogatories to restrict them to the subject matter of the particular case, to avoid undue detail, and to avoid the imposition of any unnecessary burden or expense on the answering party.
(c) Number of Interrogatories. Except as provided in subparagraph (j), a party shall not serve more than 30 interrogatories, including sub-parts, on any other party except upon agreement of the parties or leave of court granted upon a showing of good cause. A motion for leave of court to serve more than 30 interrogatories must be in writing and shall set forth the proposed interrogatories and the reasons establishing good cause for their use.
(d) Answers and Objections. Within 28 days after service of the interrogatories upon the party to whom they are directed, the party shall serve a sworn answer or an objection to each interrogatory, with proof of service upon all other parties entitled to notice. Any objection to an answer or to the refusal to answer an interrogatory shall be heard by the court upon prompt notice and motion of the party propounding the interrogatory. The answering party shall set forth in full each interrogatory being answered immediately preceding the answer. Sworn answers to interrogatories directed to a public or private corporation, or a partnership or association shall be made by an officer, partner, or agent, who shall furnish such information as is available to the party.
(e) Option to Produce Documents. When the answer to an interrogatory may be obtained from documents in the possession or control of the party on whom the interrogatory was served, it shall be a sufficient answer to the interrogatory to produce those documents responsive to the interrogatory. When a party elects to answer an interrogatory by the production of documents, that production shall comply with the requirements of Rule 214.
(f) Identity and Testimony of Witnesses. Upon written interrogatory, a party must furnish the identities and addresses of witnesses who will testify at trial and must provide the following information:
(1) Lay Witnesses. A “lay witness” is a person giving only fact or lay opinion testimony. For each lay witness, the party must identify the subjects on which the witness will testify. An answer is sufficient if it gives reasonable notice of the testimony, taking into account the limitations on the party’s knowledge of the facts known by and opinions held by the witness.
(2) Independent Expert Witnesses. An “independent expert witness” is a person giving expert testimony who is not the party, the party’s current employee, or the party’s retained expert. For each independent expert witness, the party must identify the subjects on which the witness will testify and the opinions the party expects to elicit. An answer is sufficient if it gives reasonable notice of the testimony, taking into account the limitations on the party’s knowledge of the facts known by and opinions held by the witness.
(3) Controlled Expert Witnesses. A “controlled expert witness” is a person giving expert testimony who is the party, the party’s current employee, or the party’s retained expert. For each controlled expert witness, the party must identify: (i) the subject matter on which the witness will testify; (ii) the conclusions and opinions of the witness and the bases therefor; (iii) the qualifications of the witness; and (iv) any reports prepared by the witness about the case.
(g) Limitation on Testimony and Freedom to Cross-Examine. The information disclosed in answer to a Rule 213(f) interrogatory, or in a discovery deposition, limits the testimony that can be given by a witness on direct examination at trial. Information disclosed in a discovery deposition need not be later specifically identified in a Rule 213(f) answer, but, upon objection at trial, the burden is on the proponent of the witness to prove the information was provided in a Rule 213(f) answer or in the discovery deposition. Except upon a showing of good cause, information in an evidence deposition not previously disclosed in a Rule 213(f) interrogatory answer or in a discovery deposition shall not be admissible upon objection at trial.
Without making disclosure under this rule, however, a cross-examining party can elicit information, including opinions, from the witness. This freedom to cross-examine is subject to a restriction that applies in actions that involve multiple parties and multiple representation. In such actions, the cross-examining party may not elicit undisclosed information, including opinions, from the witness on an issue on which its position is aligned with that of the party doing the direct examination.
(h) Use of Answers to Interrogatories. Answers to interrogatories may be used in evidence to the same extent as a discovery deposition.
(i) Duty to Supplement. A party has a duty to seasonably supplement or amend any prior answer or response whenever new or additional information subsequently becomes known to that party.
(j) The Supreme Court, by administrative order, may approve standard forms of interrogatories for different classes of cases.
(k) Liberal Construction. This rule is to be liberally construed to do substantial justice between or among the parties.
End
Plain-English Summary
A party can serve up to 30 interrogatories, subparts included, on any other party, without needing court permission — more than that takes agreement or a showing of good cause. Answers and any objections are due within 28 days, sworn under oath, with each answer following its own question. A party can answer by pointing to documents instead of writing out the answer, as long as production follows the document-request rules in Rule 214.
The rule's centerpiece is paragraph (f), which sorts trial witnesses into three tiers with different disclosure demands. Lay witnesses need only their expected subjects of testimony. Independent experts — like a treating doctor not retained for litigation — need subjects and expected opinions. Controlled experts — the party itself, its current employees, or its retained experts, when any of them will offer expert testimony — need full detail: subject matter, opinions, bases, qualifications, and reports.
Whatever gets disclosed under paragraph (f), or in a discovery deposition, caps what the witness can say on direct at trial — undisclosed testimony risks exclusion. Cross-examination stays freer, letting a party draw out undisclosed opinions, except when co-parties share the same position on an issue. Parties must keep answers current under a continuing duty to supplement.
Frequently Asked Questions
How many interrogatories can one party serve on another in Illinois?
Up to 30, including subparts, without leave of court; more requires agreement or a court-approved showing of good cause.
How long does a party have to answer interrogatories?
28 days from service, with sworn answers or objections to each one.
What's the difference between a lay witness, an independent expert, and a controlled expert under Rule 213(f)?
Lay witnesses need only disclosed subjects of testimony; independent experts need subjects and expected opinions; controlled experts — the party's own retained experts — need full detail on subject matter, opinions, bases, qualifications, and reports.
Can a witness testify about something not disclosed in interrogatory answers?
Generally no on direct examination — undisclosed testimony is subject to exclusion absent good cause, though cross-examination allows more latitude.
Is there a duty to update interrogatory answers as a case develops?
Yes, Rule 213(i) requires a party to seasonably supplement or amend answers whenever new information comes to light.
Comments and Related Materials
Committee Comments
(March 28, 2002)
Paragraph (f)
The purpose of this paragraph is to prevent unfair surprise at trial, without creating an undue burden on the parties before trial. The paragraph divides witnesses into three categories, with separate disclosure requirements for each category.
“Lay witnesses” include persons such as an eyewitness to a car accident. For witnesses in this category, the party must identify the “subjects” of testimony—meaning the topics, rather than a summary. An answer must describe the subjects sufficiently to give “reasonable notice” of the testimony, enabling the opposing attorney to decide whether to depose the witness, and on what topics. In the above example, a proper answer might state that the witness will testify about: “(1) the path of travel and speed of the vehicles before impact, (2) a description of the impact, and (3) the lighting and weather conditions at the time of the accident.” The answer would not be proper if it said only that the witness will testify about: “the accident.” Requiring disclosure of only the subjects of lay witness testimony represents a change in the former rule, which required detailed disclosures regarding the subject matter, conclusions, opinions, bases and qualifications of any witness giving any opinion testimony, including lay opinion testimony. Experience has shown that applying this detailed-disclosure requirement to lay witnesses creates a serious burden without corresponding benefit to the opposing party.
“Independent expert witnesses” include persons such as a police officer who gives expert testimony based on the officer’s investigation of a car accident, or a doctor who gives expert testimony based on the doctor’s treatment of the plaintiff’s injuries. For witnesses in this category, the party must identify the “subjects” (meaning topics) on which the witness will testify and the “opinions” the party expects to elicit. The limitations on the party’s knowledge of the facts known by and opinions held by the witness often will be important in applying the “reasonable notice” standard. For example, a treating doctor might refuse to speak with the plaintiff’s attorney, and the doctor cannot be contacted by the defendant’s attorney, so the opinions set forth in the medical records about diagnosis, prognosis, and cause of injury might be all that the two attorneys know about the doctor’s opinions. In these circumstances, the party intending to call the doctor need set forth only a brief statement of the opinions it expects to elicit. On the other hand, a party might know that a treating doctor will testify about another doctor’s compliance with the standard of care, or that a police officer will testify to an opinion based on work done outside the scope of the officer’s initial investigation. In these examples, the opinions go beyond those that would be reasonably expected based on the witness’ apparent involvement in the case. To prevent unfair surprise in circumstances like these, an answer must set forth a more detailed statement of the opinions the party expects to elicit. Requiring disclosure of only the “subjects” of testimony and the “opinions” the party expects to elicit represents a change in the former rule, which required detailed disclosures about the subject matter, conclusions, opinions, bases, and qualifications of all witnesses giving opinion testimony, including expert witnesses over whom the party has no control. Experience has shown that the detailed-disclosure requirement is too demanding for independent expert witnesses. “Controlled expert witnesses” include persons such as retained experts. The party can count on full cooperation from the witnesses in this category, so the amended rule requires the party to provide all of the details required by the former rule. In particular, the requirement that the party identify the “subject matter” of the testimony means that the party must set forth the gist of the testimony on each topic the witness will address, as opposed to setting forth the topics alone.
A party may meet its disclosure obligation in part by incorporating prior statements or reports of the witness. The answer to the Rule 213(f) interrogatories served on behalf of a party may be sworn to by the party or the party’s attorney.
Paragraph (g) Parties are to be allowed a full and complete cross-examination of any witness and may elicit additional undisclosed opinions in the course of cross-examination. This freedom to cross-examine is subject to a restriction that, for example, prevents a party from eliciting previously undisclosed contributory negligence opinions from a coparty’s expert. Note that the exception to disclosure described in this paragraph is limited to the cross-examining party. It does not excuse the party calling the witness from the duty to supplement described in paragraph (i).
Paragraph (i) The material deleted from this paragraph now appears in modified form in paragraph (g).
Paragraph (k) The application of this rule is intended to do substantial justice between the parties. This rule is intended to be a shield to prevent unfair surprise but not a sword to prevent the admission of relevant evidence on the basis of technicalities. The purpose of the rule is to allow for a trial to be decided on the merits. The trial court should take this purpose into account when a violation occurs and it is ordering appropriate relief under Rule 219(c). The rule does not apply to demonstrative evidence that is intended to explain or convey to the trier of fact the theories expressed in accordance with this rule.
Committee Comments
(Revised June 1, 1995)
Paragraph (a) The provision of former Rule 19-11(1) as to who is to answer interrogatories served on corporations, partnerships, and associations appears in paragraph (d) of this rule. The provisions of former Rule 19-11(1) stating that both interrogatories and depositions could be employed and that the court may issue protective orders were deleted because these matters are covered in Rules 201(a) and (c). A prior requirement that the written interrogatories be spaced so as to permit the answering party to answer upon the interrogatory served upon him has been amended to eliminate the spacing requirement, primarily because of the practical and customary way in which interrogatories are answered.
Paragraph (b) Like paragraph (a) of Rule 201, which cautions against duplication, this provision states the general policy of the rules for the guidance for the court when it is called upon to frame protective orders or dispose of objections to interrogatories as provided in paragraph (d) of Rule 213.
Paragraph (c) Paragraph (c) is new. Because of widespread complaints that some attorneys engage in the practice of submitting needless, repetitious, and burdensome interrogatories, paragraph (c) limits the number of all interrogatories, regardless of when propounded, to 30 (including subparts), unless “good cause” requires a greater number.
Paragraph (d) Paragraph (d) is derived from former Rules 19-11(2) and (3). This paragraph embodies a number of changes in the present practice. The time for answering interrogatories is fixed at 28 days instead of 30 (as in former Rule 19-11(2)), consistent with the committee’s general policy of establishing time periods that are multiples of seven days. Under former Rule 19-11(3), the time for making objections is 15 days. Paragraph (d) increases this to 28 days, making the time limit for answering and objecting the same. The other change in Illinois practice effected by paragraph (d) is the requirement that motions to hear objections to interrogatories must be noticed by the party seeking to have the interrogatories answered. Under former Rule 19-11(3) the objection must be noticed by the party making it. This change was made because the committee believes the party seeking the information should have the burden of seeking a disposition of the objection, and that this will tend to reduce the number of rulings that are necessary by automatically suspending interrogatories which a party is not seriously interested in pursuing. The last phrase provides that the person answering must furnish such information as is available to the party. This phrase was added, as was the same provision to Federal Rule 33 in 1946, to make certain that a corporation, partnership, or association may not avoid answering an interrogatory by disclaiming personal knowledge of the matter on the part of the answering official.
Paragraph (e) Paragraph (e) has been amended to require a party who elects to answer an interrogatory by referring to documents, to produce the responsive documents as part of the party’s answer. When a party elects to respond to an interrogatory by the production of documents, that production must comply with the requirements of Rule 214.
Paragraph (f) Paragraph (f) now requires a party to serve the identity and location of witnesses who will testify at trial, together with the subject of their testimony. This is a departure from the previously recognized law. This paragraph, as well as others contained in these rules, imposes a “seasonable” duty to supplement.
Paragraph (g) In light of the elimination of former Supreme Court Rule 220, the definition of an opinion witness is now a person who will offer “any” opinion testimony. It is the Committee’s belief that in order to avoid surprise, the subject matter of all opinions must be disclosed pursuant to this rule and Supreme Court Rule 218, and that no new or additional opinions will be allowed unless the interests of justice require otherwise. For purposes of this paragraph, there is no longer a distinction between retained and nonretained experts. Further, upon written interrogatories, a party must state the subject matter to be testified to, the conclusions, opinions and qualifications of opinion witnesses, and provide all reports of opinion witnesses.
Paragraph (h) Paragraph (h) is derived from former Rule 19-11(4), which provided that answers to interrogatories could be used to the same extent as the deposition of an adverse party. Under former Rule 19-11(1), interrogatories can be directed only to adverse parties; hence the provision in former Rule 19-11(4) to the effect that the answers could be used as could a deposition of an adverse party. Paragraph (a) of the new rule provides that interrogatories can be directed to any party. Accordingly, paragraph (h) of the new rule provides that the answers can be used to the same extent as a discovery deposition. Former Rule 19-11(4) also contained a statement on the scope of interrogatories, equating the permissible scope of inquiry to that permitted in the taking of a deposition. This provision was deleted as unnecessary in view of the provisions of Rule 201(b)(1).
Paragraph (i) With regard to paragraph (i), the new rule imposes a “seasonable” duty to supplement or amend prior answers when new or additional information becomes known to that party. This is a change from previous discovery requirements and thus eliminates the need for supplemental interrogatories unless different information is sought. The Committee believes that the definition of “seasonable” varies by the facts of each case and by the type of case, but in no event should it allow a party or an attorney to fail to comply with the spirit of this rule by either negligent or wilful noncompliance.
Paragraph (j) In an effort to avoid discovery disputes, the practitioner is encouraged to utilize interrogatories approved by the Supreme Court pursuant to paragraph (j) whenever possible.
Administrative Order
(Nov. 27, 2002)
In re Discovery Rules
The order entered March 28, 2002, amending various rules and effective July 1, 2002, shall apply to all cases filed after such effective date as well as all cases pending on such effective date, provided that any discovery order entered in any such case prior to July 1, 2002, shall remain in effect unless and until amended by the trial court.
Order entered November 27, 2002, effective immediately.
Amendment History
Amended July 1, 1985, effective August 1, 1985; amended June 1, 1995, effective January 1, 1996; amended April 3, 1997, effective May 1, 1997; amended March 28, 2002, effective July 1, 2002; amended December 6, 2006, effective January 1, 2007; amended Dec. 29, 2017, eff. Jan. 1, 2018.
Source & verification. Rule text, official Committee Comments, and
amendment history are reproduced verbatim from the Illinois Supreme Court Rules,
promulgated by the Supreme Court of Illinois. Last verified July 20, 2026.
· Official source
Also known as: interrogatoriesROGwritten interrogatoriesexpert witness disclosurecontrolled expert witnessFRCP 33 equivalent30 interrogatory limit