Recent Cases Limit Scope of Permissible Expert Witness Testimony

Recent federal court decisions illustrate that even highly qualified professionals may be excluded if their testimony extends beyond their demonstrated specialty. In Bard Implanted Port Catheter Prods. Liab. Litig. v. Becton Dickinson & Co., 2026 LX 155458, 10 (D. Ariz. Mar. 24, 2026), the court determined that a vascular and interventional radiologist’s extensive experience with implanted ports did not qualify him to opine on the cause of a patient’s bloodstream infection. Similarly, in Downing v. Kubota Tractor Corp., 2026 LX 97452, 7 (N.D. Ind. Feb. 10, 2026), a tractor design engineer was barred from testifying about how an alternative safety design would have affected the decedent’s injuries because those opinions exceeded his expertise.

To reduce the risk of exclusion, attorneys should evaluate an expert’s qualifications beyond formal degrees and certifications. Peer-reviewed publications, conference presentations, teaching experience, government research, consulting work, and prior expert testimony can all demonstrate expertise that extends beyond a narrow specialty. By understanding and documenting the full scope of an expert’s education, research, and professional experience, attorneys can better position their experts to withstand qualification challenges based on claims of overspecialization.

In the context of insurance bad faith, expert’s face the added paradox of attempting to opine on issues that necessarily involve legal standards without trespassing into the judge’s territory as the sole arbiter of legal conclusions. Despite this restriction, the expert’s framing of the facts can go a long way in leading the proverbial horse to water. For example, a policyholder expert in Am. Can! & Am. Can! Cars for Kids v. Arch Ins. Co. & Care Providers Ins. Servs. LLC, 2022 U.S. Dist. LEXIS 87416 (N.D. Tex. Apr. 6, 2022) was permitted to opine that the insurer “slow-walked review of the bills and raised unjustified conflicts and issues, resulting in the insured having to make the direct payments and then be left to the mercy of [the insurer] in terms of getting reimbursement.” He explained why this practice violated the terms of the agreement at issue. A second expert highlighted the deficiencies in the insurer’s reservation of rights (“ROR”) letters. The second expert also noted where the insurer failed to abide by standard practice within the industry.