Thanks for the link. For those curious, this seems to be the relevant section: Differing Requirements for Expert and Non-Retained Witnesses While non-retained

Thanks for the link. For those curious, this seems to be the relevant section: Differing Requirements for Expert and Non-Retained Witnesses While non-retained witnesses require some disclosure, expert witnesses require far more. It may be challenging to compel an expert witness to testify, in part, because before an expert witness is deposed or testifies, the federal rules require the disclosure of a report. Federal Rule of Civil Procedure 26 (a) (2) (B) calls for the disclosure of a report including: * A complete statement of all the opinions a witness plans to express, as well as the basis for the opinions, and the reasons supporting the opinions * The facts or data relied on or considered when forming the opinion * Exhibits the expert will use to support or summarize their findings * Their qualifications and the last 10 years of their publications * All other cases the witness testified as an expert, whether in trial or deposition * A statement of compensation the expert has been or will be paid for the study and testimony in the case at hand Obviously, it will be difficult, if not impossible, to obtain this information in a report from a non-compensated, unretained expert.