By Evan Weisberg and Christopher Cunio of Hunton and Kevin Cahill of FTI Consulting Inc.

In In re: Bard Implanted Port Catheter Products Liability Litigation,[1] decided by the U.S. District Court for the District of Arizona in March, the defendants sought to use a medical expert to opine on causation and diagnosis.

The medical expert, a doctor, opined that the plaintiff "developed a bloodstream infection likely due to suboptimal sterile technique by his wife and family friend at the time of flushing and deaccessing his port."[2]

The doctor was a board-certified vascular and interventional radiologist who had served as a professor at the University of California, Los Angeles; the University of Pennsylvania; the University of Texas; and the University of Michigan. Moreover, as the defendants pointed out, the doctor had "placed tens of thousands of ports" and "de-accesses ports frequently."[3]

The plaintiff challenged the doctor's qualifications to offer an opinion on causation, and the court agreed with the plaintiff. Despite the expert's credentials and experience as a vascular and interventional radiologist, the court found that the expert's "familiarity with ports does not necessarily render him qualified to opine on the cause of a blood infection."[4]

In another recent case, Downing v. Kubota Tractor Corp.,[5] decided by the U.S. District Court for the Northern District of Indiana on March 2, the plaintiff attempted to introduce an expert to opine about, among other things, the feasibility of an alternative design of a tractor that had caused the death of its operator.

The proposed expert had almost 30 years of experience in the engineering and design of tractor components, and had served as an expert on tractor design previously.[6]

The defendant argued that the proposed expert was not qualified "to testify on how an alternate [Operator Presence Control module] design could have affected" the victim's injuries.[7] The court agreed, finding that, despite the expert's credentials in engineering and design of tractor components, the expert's testimony went "beyond opinions on engineering and design."[8]

Both of these cases highlight the potential for highly specialized experts to be vulnerable to exclusion because the breadth of their expertise could be narrow.

In this article, we address the topic of overspecialization by first explaining the types of subspecialties and qualifications that can exist within fields. We then describe how peer-reviewed publications, conference presentations and other professional activities can support an expert's testimony about general topics within their field, even if the expert has a particular specialty or focus.

The first point to make is that, even when it comes to basic qualifications within a field, differences can exist by degree types. Some differences in degree types are well known, such as an M.D. or D.O. degree for medical doctors. Others are less well known, such as a Ph.D. and Psy.D. degree in psychology, both of which confer the title "doctor" on those who receive it.

In fields such as sociology and economics, by contrast, a Ph.D. is the only doctoral degree. While important in certain contexts, the distinction between types of doctoral degrees within a field is typically not a contentious topic when it comes to expert testimony.

What tends to be a source of contention, however, is the wide variation in specialties and subspecialties that exists within degree types, because an opposing attorney might claim that an expert's knowledge is limited to their specialty or subspecialty.

This argument can have merit in some situations. Consider a case where a proposed expert holds a degree in economics. Whereas one expert in economics might focus on macroeconomics, the study of economies at the aggregate level, another might focus on microeconomics, the study of firm- and individual-level decision-making.

The expert who focuses on macroeconomics might be vulnerable to exclusion, for example, if their work focuses primarily on the monetary policy of the Federal Reserve Bank, yet they intend to offer opinions in a case related to microeconomics, such as an employment discrimination case.

The difference between macroeconomics and microeconomics is just the tip of the iceberg, too. A host of subspecialties exist within both macroeconomics (e.g., monetary economics, fiscal policy, public finance, development economics) and microeconomics (e.g., consumer behavior, industrial organization, labor economics, environmental economics).

A similar dynamic exists with certifications. Take the field of accounting as an example. While a Ph.D. in accounting exists, a doctoral degree is not required to achieve a certified public accountant certification, and CPAs are routinely called to provide expert testimony on accounting issues.

A plethora of other certifications exist for accountants and engineers. Other fields have licenses that are required for individual private practice, such as psychology, and still others have no certifications at all, like economics.

One additional layer of complexity is when experts have two or more areas of specialization or multiple certifications. In economics, for example, it is not uncommon for a microeconomist to claim expertise in healthcare, labor economics and econometrics.

A business valuation expert might be accredited in business valuation, be a certified valuation analyst and be certified in financial forensics. In these circumstances, opposing attorneys can leverage the existence of multiple areas of specialization to argue that an expert has limited expertise outside of those areas, even if they have the education, training and experience to testify on broader issues.

The first line of defense against such arguments is awareness. Attorneys who work with experts should be aware of the various combinations of specialties, subspecialties and certifications that exist within the expert's field, and how the expert's background fits within them.

In some instances, the distinctions are obvious. Attorneys are unlikely to put forth a doctor specializing in obstetrics and gynecology to opine on standard practice and procedures for open-heart surgery. Attorneys are also unlikely to put forth a tax accountant to opine about a real estate case.

The distinctions are less clear-cut in other specialties. Is it reasonable for a clinical psychologist to opine about issues related to industrial psychology? Is it reasonable for a doctor of internal medicine to opine on pediatrics? Here, a conversation with your expert about the depth and breadth of their expertise within their field might be worthwhile.

A second line of defense is to review what your expert has published, and the areas covered in those publications. It might be the case that an expert has published primarily on one topic, but has also published in other areas that can bolster their qualifications to opine on broader topics.

When it comes to publications, it is also important to understand what qualifies as a peer-reviewed article. Peer review is a process in which an article submitted to a journal gets reviewed by an editor and is either not accepted for publication or sent out for review to a set of reviewers who are experts in the field.

The reviewers read the article and provide a detailed critique in writing to the editor. The editor then summarizes these critiques and either requests a revision, rejects the article, or, in rare cases, accepts the article outright. The revise and resubmit process can be iterative and take upward of one year. Generally, only after the reviewers are satisfied with the author's responses will an article be accepted by the journal for publication.

If an author receives a desk reject from a journal or is unable to satisfy the reviewers, the next step is to submit the article to a different journal, typically of a lower status, in the hope that the article will be accepted by that journal.

This process is one reason to consider not just whether an expert has been published in peer-reviewed publications, but also the status of the journal. Also, other publications such as book chapters (typically not peer-reviewed but reviewed by an editor) and working papers or issue briefs (typically not peer-reviewed and not reviewed by an editor) can help bolster an expert's qualifications in areas inside and outside their specialty or subspecialty.

In addition, authors commonly present their papers at academic seminars and conferences as they navigate their way through the peer-review process. These seminars and conferences can be highly competitive, and acceptance to a prestigious conference can be another qualification for expert testimony, even if a paper has not been published.

Finally, beyond degrees and publications, the expert's work experience can serve as a basis for offering opinions. Experts' work experience can be grouped into three sectors: academic (e.g., professors), government and private (e.g., consulting).

For academics, courses taught can be indicative of expertise beyond research interests. For government, research can consist of government reports or projects on which an expert worked, and these activities can serve as additional support for offering expert opinions.

Private consultants can use client projects and, if working in the litigation space, past expert testimony as a basis for offering opinions that might fall outside of a particular specialty but within the scope of their formal education and training.

Specialization is common among experts and, as a result, they can be exposed to potential exclusion if their testimony relates to their field generally instead of their specialty specifically. Attorneys can mitigate this exposure by understanding how their expert's qualifications and specialization fit within their overall field.

[1] In re: Bard Implanted Port Catheter Prods. Liab. Litig. , 2026 WL 818040 (D. Ariz. Mar. 25, 2026).

[2] Id. at *3.

[3] Id. at *2.

[4] Id. at *4.

[5] Downing v. Kubota Tractor Corp. , 2026 WL 574913 (N.D. Ind. Mar. 2, 2026).

[6] Id. at *2.

[7] Id. at *3.

[8] Id.

Originally published on June 24, 2026 with Law360. Reprinted with permission. Further duplication without permission is prohibited. All rights reserved.

The opinions expressed are those of the author(s) and do not necessarily reflect the views of the firm, its clients, or Portfolio Media Inc., or any of its or their respective affiliates. This article is for general information purposes and is not intended to be and should not be taken as legal advice.