Defense Digest, Vol. 30, No. 2, June 2024

Experts in Defense: Delaware Superior Court Agrees that Expert Witnesses Must Opine Beyond Mere Speculation to Meet Basic Causation Requirements and the Opinion Must Be Unequivocal

Key Points: 

  • Expert medical testimony must be offered unequivocally to support causation in medical negligence cases. 
  • Counsel cannot bolster the expert testimony required to establish causation through argument—expert testimony alone must lay this ground.
  • Summary judgment in favor of the defense is proper where the plaintiff fails to offer an unequivocal expert opinion with reasonable medical probability regarding negligence or causation. 

Marshall Dennehey’s health care defense attorneys in the Wilmington, Delaware, office recently succeeded in arguing a motion for summary judgment in the Delaware Superior Court. In Trott v. Cessna, 2024 WL 658859 (Del. Super. Feb. 16, 2024), the court held that unequivocal expert medical testimony must be offered with reasonable medical probability or certainty to connect a defendant-nurse’s negligence to the plaintiff’s injury. 

The plaintiff alleged that the defendant-nurse failed to provide him with proper and timely medical care and treatment and in such a manner that amounted to negligence and breaching the standard of care. However, upon the defense’s motion raising the insufficiency of expert opinions, the court found that the plaintiff failed to offer the necessary opinion to establish causation between the defendant-nurse’s failings and the plaintiff’s injury. Specifically, the plaintiff alleged that there was a delay in treating him for stroke symptoms and that, as a result, he was permanently disabled. The issue as to causation was whether the timing of the nurse’s involvement would have made any impact on the plaintiff’s outcome, even if the symptoms had been reported, as the plaintiff suggests should have occurred. 

A plaintiff bears the burden of presenting unequivocal expert medical testimony on two fronts—deviation from the applicable standard of care and causation between the alleged wrongful conduct and the alleged injury. Specifically, “a jury is not permitted to connect the dots between a bare allegation of medical negligence and an injury.” Trott, 2024 WL 658859, at *17.

The Trott court held that while the plaintiff satisfied the first requirement of establishing a deviation from the standard of care, he failed to offer sufficient expert medical opinion that any alleged violation proximately caused his alleged injury. Specifically, the plaintiff’s nursing expert adequately opined about a failure to adhere to the applicable standard of care. However, his expert neurosurgeon testified that “he could not opine that the nurse’s deviations from the standard of care more likely than not changed the outcome” of the plaintiff’s injury. Id. at *21. 

The defense argued in their motion for summary judgment that the plaintiff’s lack of a sufficient expert opinion related to causation, as indicated by the expert’s report, deposition and supplemental report, was sufficient grounds to dismiss the claims against their defendant-nurse. In fact, it was clear that the plaintiff’s standard of care experts had conflicting opinions, and the plaintiff had only one causation expert, who affirmatively testified that he would not opine that there was any connection between the defendant-nurse’s care and the plaintiff’s alleged injury. 

The plaintiff responded that, because his doctor-expert’s testimony on the causation issue was equivocal, this established an issue of material fact. However, the Delaware Superior Court disagreed, stating that the plaintiff’s expert’s equivocation amounted to speculation at best, which was insufficient to meet the standard required by Delaware Code Title 18 Section 6853(e) to establish causation through expert medical testimony. This decision reaffirms the importance of unequivocal expert testimony being offered based on a reasonable degree of medical probability or certainty. 

*Tom, Brad and Lisa work in our Wilmington, Delaware, office. 


Defense Digest, Vol. 30, No. 2, June 2024, is prepared by Marshall Dennehey to provide information on recent legal developments of interest to our readers. This publication is not intended to provide legal advice for a specific situation or to create an attorney-client relationship. ATTORNEY ADVERTISING pursuant to New York RPC 7.1. © 2024 Marshall Dennehey. All Rights Reserved. This article may not be reprinted without the express written permission of our firm. For reprints, contact