Lessons In Retaining The Right Medical Expert: You May Not Need The Specialty, But You Certainly Need The Relevant “Skills and Experience”


Gastroenterology Expert

Court: Court of Appeal of California, Second Appellate District, Division Three
Jurisdiction: Federal
Case Name: Wilson v. McKesson Corp.
Citation: 2017 Cal. App. Unpub. LEXIS 574

In this products liability case, the plaintiffs accused AstraZeneca Pharmaceuticals LP and McKesson Corporations of negligence and fraud in their marketing of the drug, Nexium. The case alleged that the proton pump inhibitor (PPI) for peptic ulcers and gastroesophageal reflux, causes bone deterioration, osteoporosis, and bone fractures.

Although the likely choices for an expert witness might have been an epidemiologist, a bone biologist, or a gastroenterologist, the plaintiff’s designated an orthopedic surgeon as their expert. The court ultimately found that the expert was not qualified to opine on causation, however, not because of his specialty in orthopedic surgery, but because of his lack of “special knowledge, skill, experience, training, or education” regarding the effect of PPIs on bone deterioration.

The Expert

The plaintiff’s causation expert witness was an orthopedic surgeon specializing in hip and knee replacements. In spite of his lack of experience in epidemiology or gastroenterology, the expert drafted a report in which he opined that proton pump inhibitors cause fractures by compromising calcium intake. The expert also indicated that he relied almost entirely upon medical literature, particularly epidemiological studies, in order to render his opinion.


The defendants moved to exclude the testimony the plaintiff’s orthopedic surgeon expert asserting that the expert was not qualified because he lacked “special expertise” in epidemiology and the metabolism of PPIs.

Upon digging into the expert’s background, it was determined that he had never prescribed Nexium or any other PPIs. He had not studied the impact of PPIs on bones. The expert also admitted he did not understand how proton pump inhibitors compromised calcium intake, nor how they are metabolized. When asked about how PPIs could cause bone deterioration — the root issue of causation for the case — the expert stated he would need to “defer to experts in gastroenterology, epidemiology, or endocrinology.”

The federal court subsequently granted the defense’s motion to exclude the orthopedic surgeon expert’s opinions on causation as unreliable, stating that the expert’s causation report “amounted to guesswork”. The court referenced the California Supreme Court’s decision in Sargon Enterprises, Inc. v. University of Southern California (2012) 55 Cal.4th 747, 149 Cal. Rptr. 3d 614, 288 P.3d 1237, under which expert testimony was excluded for the same reason.


On appeal, the plaintiffs argued that their expert was, in fact, qualified to opine on causation because of his expertise as “an orthopedic surgeon who regularly treats bone fractures, a professor of orthopedic surgery, a trained physician, and the author of numerous scientific articles in the field of orthopedics.”

However, the court reiterated that the expert’s qualifications must be related to the particular subject on which they are giving expert testimony. In this case, because the causation testimony sought to specifically address the impact of PPI ingestion on bone integrity (not the treatment of bone fractures), acceptable specialized training could have included epidemiology, bone biology, endocrinology, gastroenterology, or vitamin and mineral metabolism.


Ultimately, the court felt that the expert’s opinion on causation fell well outside of his experience, training, and education. The expert failed to evaluate any factors relevant to determining whether Nexium causes bone deterioration, osteoporosis, or bone fractures. What’s more, the expert’s entire opinion and expert report were based on summaries of epidemiological studies rather than hands-on experience. And when asked about the epidemiological studies on which he relied, the expert was not proficient enough in the relevant medical field to respond.

Thus, the expert’s opinion failed to assist the trier of fact in determining whether Nexium caused the injuries. The trial court did not abuse its discretion in finding that the expert’s education, training, and experience in orthopedic surgery and in general as a physician were insufficient to qualify him as the causation expert.

Key Takeaways

  1. Although a physician is permitted to give opinions outside of their expertise, the physician must still demonstrate that they possess skills and experience that qualify them to discuss the subject matter of their testimony.
  2. Experts should not base their entire testimony on summaries of the medical literature.