Tort lawyers in the United States often think of “loss of a chance” as a theory of “probabilistic causation” that only applies to medical malpractice misdiagnosis cases. The theory is that if a physician negligently fails to diagnose a curable disease, and the patient is harmed by the disease, the physician should be liable for causing the “loss of a chance” of a cure. We shall see that if the chance of a cure is less than 50 percent, the plaintiff cannot prove by a preponderance of evidence that the negligence caused the harm, and would recover no damages under the traditional “all or nothing” rule. Loss of a chance becomes a theory of “probabilistic causation” if we use it to hold the physician liable for the patient's harm but reduce any award by the chance that the harm would have occurred even with proper diagnosis and treatment. If, for example, the chance of a cure was 40 percent, under a “probabilistic causation” rule, the physician would be liable for 40 percent of the patient's harm because the physician deprived the patient of a 40 percent “chance” of avoiding the harm.
David A. Fischer, Tort Recovery for Loss of A Chance, 36 Wake Forest L. Rev. 605 (2001)