Illinois Rules Regarding Expert Witness Depositions and Interrogatories 

Testifying experts may be subject to deposition in Illinois. Under Rule 206(d) of the Illinois Supreme Court Rules, depositions are generally limited to three hours. Experts retained only for consulting purposes, on the other hand, may only be subject to discovery under exceptional circumstances as described below, and, as such, are generally protected from deposition. Additionally, under Rule 204(c), physician experts are exempt from the general permissibility of depositions, and may only be deposed upon “agreement of the parties and the subsequent consent of the deponent or under a subpoena issued upon order of court.”

Neither consulting experts nor testifying experts may be subject to interrogatories in Illinois as they may only be served on the parties themselves.

Illinois Expert Witness Reports and Disclosures Rules 

The Illinois Supreme Court Rules distinguishes between consultants and experts who will provide testimony at trial. Under Rule 201(b)(3), experts retained only for consulting purposes are fully protected from discovery except upon a showing of exceptional circumstances under which it is impracticable for the party seeking discovery to obtain facts or opinions on the same subject matter by other means. The Committee Comments to Rule 201(b)(3) explain that such exceptional circumstances may be found “in cases in which an item of physical evidence is no longer available because of destructive testing and the adversary’s consultant is the only source of information about the item, or in cases in which all the experts in a field have been retained by other parties and it is not possible for the party seeking discovery to obtain his or her own expert.”

For testifying experts, Rule 213(f) of the Illinois Supreme Court Rules further distinguishes between “independent expert witnesses,” who are experts that are not parties, current employees of parties, or experts retained by the parties, and “controlled expert witnesses,” who are parties, current employees of parties, and experts retained by the parties. For independent experts, upon a written interrogatory, a party must disclose the identity and address of the expert, the subject matter of the expert’s testimony, and the opinions to which the expert is expected to testify. For controlled experts, upon a written interrogatory, a party must disclose the same information as required for independent experts plus the qualifications of the expert and any reports prepared by the expert about the case. 

Rules Regarding Lawyer-Expert Communications, Draft Expert Witness Reports, Expert Witness Notes, Etc. in Illinois 

There is no case law or rule in Illinois dealing directly with the discovery of testifying experts’ draft reports or communications between such experts and attorneys. However, given the broad scope of discovery allowed under Rule 201(b) of the Illinois Supreme Court Rules and the absence of explicit protections of such materials from discovery, several Illinois practice guides recommend that parties should assume this information can be discovered. See, e.g., 1-14 Illinois Civil Procedure § 14.06 (2014); Andrew W. Vail & Colleen G. DeRosa, Illinois Civil Practice Guide, Jenner & Bock LLP  (2012). Additionally, at least one Illinois guide suggests a form expert discovery interrogatory that requests draft reports. See S. Ct. 204(8) Expert Riders-Forms, 13 ILPRAC Rule 204(8) (2008).

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SEAK is the expert witness training company, and we’re here to help experts. We have many Free Resources For Experts.  There’s a number of things available for download there. We have a number of books for experts that we’ve published. We put on training seminars for experts three or four times a year in various parts of the country. We have a directory for expert witnesses. We have over 2000 experts listed on the directory, so they can place themselves on the directory and they can get cases. That’s on

We work one-on-one with expert witnesses to help them grow and expand their practices, be better, be more effective, help them with their expert reports, and assist them with their expert depositions. If you’re an expert witness, and you’re looking to get better, you’re looking to get more business, we’re here to help.