.png)
A battle is won or lost before it’s ever fought. So is a jury trial. Effective trucking defense attorneys should look for opportunities to challenge a plaintiff’s case early, particularly through procedural and evidentiary rules. Federal court provides a great opportunity to limit a plaintiff’s expert medical testimony when counsel is unfamiliar with the nuances of federal disclosure requirements.
This article focuses on how those rules, specifically Rule 26(a)(2), can be used to bar, restrict, or otherwise limit expert medical testimony in cases pending in the federal courts within the Seventh Circuit.
Contesting Medical Expert Disclosures
The disclosure requirements under the Federal Rules of Civil Procedure differ in important ways from many state court disclosure rules. These differences are not always obvious, but they can significantly affect how a plaintiff must disclose and ultimately present expert medical testimony.
Federal Rule of Civil Procedure 26(a)(2) governs expert disclosures in federal court and sets forth different requirements depending on whether the expert is retained. See F.R.C.P. 26(a)(2)(B); F.R.C.P. 26(a)(2)(C).
Parties must specifically disclose expert witnesses and properly designate them under the applicable subsection of Rule 26. See Karum Holdings LLC v. Lowe’s Cos., 895 F.3d 944, 950-51 (7th Cir. 2018). Failure to properly disclose expert testimony generally results in exclusion unless the failure was substantially justified or harmless. See F.R.C.P. 26(c)(1); Tribble v. Evangelides, 670 F.3d 753, 758 (7th Cir. 2012).
Medical testimony is generally considered expert testimony. See Tribble, 670 F.3d at 758-59; Rivera v. Aerovias de Mexico, S.A. de C.V., 2023 U.S. Dist. LEXIS 143260, at *6 (N.D. Ill. Aug. 16, 2023). Treating physicians may testify regarding their observations, diagnoses, and treatment under Federal Rule of Evidence 701, but opinions extending beyond those subjects may require expert disclosure. See Garcia v. North Chi. Police Officer Muhammad Alka, 2022 U.S. Dist. LEXIS 10478, at *12 (N.D. Ill. Jan. 20, 2022).
Causation opinions regarding whether an incident caused an injury or necessitated treatment are also typically considered expert testimony. See Friedman v. Cent. Me. Power Co., 2026 U.S. App. LEXIS 12356, at *18 (1st Cir. Apr. 29, 2026); Levingston v. Myles, 2022 U.S. Dist. LEXIS 58343, at *13 (N.D. Ill. Mar. 30, 2022). Excluding causation testimony based on improper disclosure can be devastating to a plaintiff’s case.
Understanding the distinction between the two categories of expert witnesses under Federal Rule of Civil Procedure 26(a)(2) is critical when evaluating and challenging a plaintiff’s expert disclosures. As discussed below, the two categories not only carry different disclosure requirements, but may also affect the scope of permissible testimony.
Witnesses Required to Be Disclosed Under Rule 26(a)(2)(B)
Rule 26(a)(2) distinguishes between experts who are required to provide written reports and those who are not. The disclosure requirements for witnesses required to provide reports are significantly more extensive, and failure to comply with those requirements can result in exclusion of the witness or limitation of the witness’s opinions. See Bellas v. Orthofix, Inc., 2016 U.S. Dist. LEXIS 138735, at *5 (N.D. Ill. Oct. 6, 2016); Doe v. City of Chicago, 2019 U.S. Dist. LEXIS 180496, at *7-8 (N.D. Ill. Oct. 18, 2019).
The rule does not always clearly define when a witness is considered “retained or specially employed to provide expert testimony.” The committee comments to Rule 26(a)(2) generally contemplate that treating physicians ordinarily are not required to provide written reports. The 2010 committee comments explain:
“A witness who is not required to provide a report under Rule 26(a)(2)(B) may both testify as a fact witness and also provide expert testimony under Evidence Rule 702, 703, or 705. Frequent examples include physicians or other health care professionals and employees of a party who do not regularly provide expert testimony.”
In practice, however, the distinction is not always straightforward. In the modern age of billboard personal injury litigation, plaintiffs are often referred to physicians who may provide not only treatment, but also litigation-oriented opinions extending beyond the scope of care provided. Courts have grappled with when such a treating physician crosses the line from a non-retained expert under Rule 26(a)(2)(C) to a retained expert subject to Rule 26(a)(2)(B). See Johnson v. Friesen, 79 F.4th 939, 944 (8th Cir. 2023) (treating physician became a retained expert required to provide a report after plaintiff’s counsel specifically requested causation opinions).
One court has suggested that the key distinction between witnesses disclosed under Rule 26(a)(2)(B) and Rule 26(a)(2)(C) is whether the witness possesses first-hand knowledge of the underlying events. See Canania v. Dippold, 2024 U.S. Dist. LEXIS 199381, at *7 (S.D. Ill. Oct. 31, 2024). The court explained:
“A witness that has first-hand knowledge of the case by being, for example, a treating physician, can provide expert testimony as it relates to their treatment and prognosis, but they are not an expert witness for the purposes of Rule 26. Whereas a lay witness’s testimony informs the jury on the happenings within a case, an expert witness’s testimony explains that information or translates, for lack of a better word, sophisticated information into information the layman can easily understand. An expert is sought for their knowledge and ability to explain things to a jury, they are not sought for their first-hand knowledge of the case. In sum, it seems that it is first-hand knowledge of the case that is the dispositive factor in determining whether a witness could be classified as an expert or lay witness.”
Other courts have similarly focused on the witness’s involvement in the underlying events. See Caruso v. Bon Secours Charity Health Sys., 703 Fed. Appx. 31, 33 (2d Cir. 2017) (“the relevant distinction is between an expert who happened to have personal involvement with the events giving rise to the litigation and an expert whose only involvement consists of aiding the already-initiated litigation”); Prieto v. Malgor, 361 F.3d 1313, 1318 (11th Cir. 2004) (employee with no involvement in the underlying events who offered opinions based solely on document review was required to provide an expert report).
Other courts have focused on the nature and scope of the opinions being offered when determining whether a witness must provide a written report under Rule 26(a)(2)(B). See Crawford v. Biolife Plasma Servs. L.P., 2011 U.S. Dist. LEXIS 60690, at *8 (N.D. Ind. June 3, 2011). Crawford also suggested that a treating physician disclosed under Rule 26(a)(2)(C) may be limited to testimony based on actual firsthand knowledge acquired during treatment. Id. at *12. See also Johnson v. Friesen, 79 F.4th 939, 944 (8th Cir. 2023) (excluding treating physician’s causation opinions where the opinions were requested by plaintiff’s counsel after treatment).
Another court concluded that the relevant inquiry requires “an examination of the nature of the witness’s relationship with the party proffering his testimony.” City of Evansville v. Envtl. Mgmt. Corp., 2012 U.S. Dist. LEXIS 204636, at *4-5 (S.D. Ind. Feb. 17, 2012). See also Bell v. Ill. Cent. R.R., 2006 U.S. Dist. LEXIS 90445, at *14 (S.D. Ill. Dec. 14, 2006); Cedant v. United States, 75 F.4th 1314, 1322 (11th Cir. 2023) (“A party retains someone for a purpose, and that purpose is most naturally defined at the beginning of the relationship…”).
Taken together, these cases suggest that witnesses disclosed under Rule 26(a)(2)(C) will generally be permitted to testify regarding their own observations, firsthand knowledge, and opinions formed during treatment. See Lilly v. United States, 2018 U.S. Dist. LEXIS 200868, at *8 (S.D. Ind. Nov. 28, 2018); Yafeng Zhu v. Keeley & Sons, Inc., 2026 U.S. Dist. LEXIS 13200, at *8-10 (S.D. Ill. Jan. 23, 2026). Opinions extending beyond those subjects, however, are less likely to be permitted. See Section II.B, infra.
The precise boundary between Rule 26(a)(2)(B) and Rule 26(a)(2)(C) testimony remains unsettled and often varies by jurisdiction. Defense counsel should therefore consider arguing that a plaintiff’s “friendly” treating physicians are, in reality, retained experts subject to the reporting requirements of Rule 26(a)(2)(B). At the same time, counsel should expect plaintiffs to argue that treating physicians fall within Rule 26(a)(2)(C) regardless of the extent of their involvement with counsel or the scope of their opinions. As always, the most persuasive arguments will be grounded in the controlling authority of the relevant jurisdiction.
Expectations should be tempered, however. None of the cases reviewed by the authors completely barred testimony from a physician who actually treated the plaintiff or otherwise possessed firsthand knowledge of the relevant facts solely because the witness was disclosed under Rule 26(a)(2)(C) rather than Rule 26(a)(2)(B). Nevertheless, these arguments can still be valuable in limiting the scope of the witness’s testimony.
Challenging the Scope of a Treating Physician’s Testimony
Even if the court rejects an argument that a treating physician was required to provide a written expert report under Rule 26(a)(2)(B), that does not end the analysis. Federal courts frequently hold that a treating physician disclosed under Rule 26(a)(2)(C) may not offer opinions extending beyond the scope of treatment or firsthand observations. See Levingston v. Myles, 2022 U.S. Dist. LEXIS 58343, at *12-13 (N.D. Ill. Mar. 30, 2022); Moriconi v. Koester, 2015 U.S. Dist. LEXIS 8486, at *3 (C.D. Ill. Jan. 26, 2015); Bell v. Ill. Cent. R.R., 2006 U.S. Dist. LEXIS 90445, at *13 (S.D. Ill. Dec. 14, 2006); Yafeng Zhu v. Keeley & Sons, Inc., 2026 U.S. Dist. LEXIS 13200 (S.D. Ill. Jan. 23, 2026) (“courts routinely limit the testimony of treating physicians when the physician is solely testifying as that of a fact witness”); United States v. Betro, 115 F.4th 429, 451 (6th Cir. 2024); Cedant v. United States, 75 F.4th 1314, 1318 (11th Cir. 2023); Jackson v. Conway, 763 F.3d 115, 126 (2d Cir. 2014).
Determining which opinions fall within the scope of treatment is highly fact-specific and not always clear. The issue is further complicated because medical experts are generally permitted to rely on information outside their own personal observations. See F.R.E. 703; Walker v. Soo Line R. Co., 207 F.3d 581, 588 (7th Cir. 2000) (“[m]edical professionals have long been expected to rely on the opinions of other medical professionals in forming their opinions”); Vanderlaan v. Ameriprise Auto & Home Ins., 2021 U.S. Dist. LEXIS 185187, at *12 (D. Colo. Sept. 28, 2021) (treating physician permitted to testify regarding other providers’ treatment, diagnoses, and prognoses when considered during treatment).
The case law nevertheless provides useful guidance for challenging the scope of a treating physician’s testimony.
Some courts have taken the position that causation opinions necessarily constitute expert testimony beyond the permissible scope of a non-retained treating physician. See Levingston, 2022 U.S. Dist. LEXIS 58343, at *12-13; Griffith v. Northeast Ill. Reg’l Commuter R.R. Corp., 233 F.R.D. 513, 516 (N.D. Ill. 2006). Under this line of cases, a plaintiff who fails to disclose a retained expert under Rule 26(a)(2)(B) may be precluded from offering causation testimony altogether.
Those decisions, however, appear to represent the minority view, and several predate the 2010 amendments to Rule 26(a). Other courts have allowed treating physicians to offer at least some causation testimony without a written report. See Liss v. TMS Int’l LLC, 2022 U.S. Dist. LEXIS 108832, at *12 (S.D. Ill. June 17, 2022); United States v. Betro, 115 F.4th 429, 451 (6th Cir. 2024) (allowing testimony on issues “covered in ordinary medical training” that fell within a “permissive core on issues pertaining to treatment”); Cedant, 75 F.4th at 1325.
Even so, there is still a strong basis to argue that certain causation opinions should be excluded. Where a court is unlikely to completely bar a treating physician’s testimony, defense counsel can still argue that the physician should be limited to opinions concerning the reasonableness of his or her own treatment and the treatment personally overseen, rather than opinions regarding the care provided by unrelated medical providers. The authors recently obtained such a ruling in the Northern District of Illinois in a January 2026 trial involving these issues.
To the extent [physician] simply summarizes plaintiff’s [general] treatment history, the Court finds that [physician] may only testify as to this information as it relates to his treatment… That is, unlike a retained expert, who might evaluate the full treatment history and offer particular opinions as to his overall treatment, causation, injuries and related matters, [physician]’s testimony will be limited to his treatment of [plaintiff], her medical history that informed his treatment decisions, and his opinions as identified in his report.
Accordingly, to the extent a physician offers opinions outside the scope of actual treatment but based on information reviewed during treatment, courts may permit that testimony.
Challenging Opinions Under Federal Rule of Evidence 702
Even where a treating physician is permitted to testify generally, defense counsel should still consider challenging specific opinions under Federal Rule of Evidence 702 on the basis that the opinions are unreliable. A full discussion of Rule 702 challenges is beyond the scope of this article, but a brief overview is warranted because issues relating to expert disclosure and reliability are often closely intertwined.
Importantly, the current version of Rule 702 took effect on December 1, 2023. See West v. Home Depot U.S.A., Inc., 2024 U.S. Dist. LEXIS 76437, at *5 (N.D. Ill. Apr. 26, 2024). The amendment was intended to emphasize that expert testimony is admissible only when the proponent demonstrates that it is more likely than not that the testimony satisfies the rule’s admissibility requirements. Id. As a result, courts are expected to scrutinize unsupported or speculative expert opinions more carefully.
Although the amended rule is relatively new and the body of case law remains limited, several issues are worth particular attention.
First, evidence of prior injuries or medical conditions that were not disclosed to the treating physician may support exclusion of causation opinions as unreliable. See West, 2024 U.S. Dist. LEXIS 76437; Barth v. United States, 2025 U.S. Dist. LEXIS 191960, at *32-33 (E.D.N.Y. Sept. 29, 2025); Viterbo v. Dow Chem. Co., 826 F.2d 420, 423 (5th Cir. 1987). But see Stockton v. CNH Indus. Am., LLC, 2018 U.S. Dist. LEXIS 229029, at *7 (N.D. Okla. May 18, 2018) (failure to review prior medical history did not render causation opinion inadmissible).
Second, permanency opinions should also be carefully scrutinized. See Passarella v. NFI Interactive Logistics, LLC, 2016 U.S. Dist. LEXIS 145500 (N.D. Ill. Oct. 20, 2016); Magnuson v. Trulite Glass Aluminum Sols., LLC, 2024 U.S. Dist. LEXIS 50736 (N.D. Ill. Mar. 21, 2024).
Third, some jurisdictions require physicians to perform an independent causation assessment during treatment before causation opinions will be admitted. See Avalos v. Miller, 2023 U.S. Dist. LEXIS 101502, at *11-14 (S.D. Tex. Apr. 14, 2023); McNabney v. Lab. Corp. of Am., 153 Fed. Appx. 293, 295 (5th Cir. 2005). In some cases, that assessment may require the physician to rule out alternative causes. Counsel should therefore explore during deposition whether an independent causation analysis was performed, when it occurred, and whether it was necessary as part of treatment.
Finally, billing opinions should also be challenged where appropriate under the applicable jurisdiction’s law, particularly when offered by a treating physician. Admission of medical bills in federal court is often governed by state law. See Stephen v. Home Depot U.S.A., 2021 U.S. Dist. LEXIS 208767, at *16. Billing opinions are arguably outside the scope of medical treatment and may therefore be vulnerable to exclusion.
Turn Disclosure Deficiencies Into Strategic Advantages
These strategies can be highly effective in identifying weaknesses in a plaintiff’s expert disclosures and creating serious advantages as trial approaches. At the same time, a thorough understanding of these rules and tactics can help defense counsel avoid similar challenges to their own expert testimony.
These arguments should be developed well in advance of trial and deployed strategically. As any trial attorney knows, preparation time becomes increasingly limited in the days leading up to trial. Identifying disclosure deficiencies and evidentiary weaknesses during that critical period can affect motions in limine, alter settlement posture, and significantly impact the presentation of the plaintiff’s case at trial.
