Paul Stephan

Proving Causation in Clinical Research Negligence

Virginia Law Review


Investigators conducting clinical research create a risk of harm to their human subjects. The common law recognizes a variety of duties that these investigators owe to their subjects. When they breach these duties, such as by negligently designing the study or failing to obtain informed consent, subjects who experience a negative outcome relative to not having participated in the study should be able to maintain a cause of action for negligence against the investigators.

Yet when researchers are negligent, it will often be impossible to show whether the study caused any individual subject’s injuries. The infamous SUPPORT study, in which researchers should have reasonably foreseen that they were exposing randomly selected infants to a higher risk of death, is one example. As the subsequent litigation over that study showed, traditional principles of causation operate to make it difficult or impossible for research subjects to pursue such claims against investigators. This is because the factual circumstances of most clinical research preclude individual plaintiffs from being able to show that their injuries were more-likely-than-not caused by their participation in the study.

The loss of chance doctrine developed in medical malpractice suits provides one potential solution for overcoming this causation problem. An even better solution, which provides optimal deterrence and as-good-as-possible compensation for injured subjects, would be for courts to adopt a theory of “marginal causation,” which permits proof of causation by the aggregate marginal damages suffered by plaintiffs as a group, as an extension of the existing doctrines of loss of chance and alternative liability.


Paul B. Stephan, Proving Causation in Clinical Research Negligence, 108 Virginia Law Review 535-579 (2022).

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