P ruitt v Lewis, Super Ct No. 08C-03-033 (Del 3/10/2011) , is interesting because it addresses the question of whether statistical evidence can be admitted to prove that a defendant did or did not breach a standard of care. The defendant offered the statistical evidence to show that there was a lack of causation and the probability that he did not breach the standard of care, because the result of his ministrations to the patient fell within expected statistical parameters.

Citing Timblin v Kent General Hospital, 640 A2d 1021 (Del 1994) , the court related the following facts. The plaintiff entered the hospital complaining of chest pains. He was diagnosed as suffering from a heart attack and was admitted to the coronary care unit. He was treated via blah, blah, blah, but ultimately suffered cardiac arrest, was deprived of oxygen for about 25 minutes, was resuscitated but suffered residual brain damage, and ultimately expired. At trial, the hospital proffered expert testimony that (1) when patients suffer cardiopulmonary arrest in a hospital, less than half will survive; (2) a review of 2 peer-reviewed articles on the subject showed that treatments of in-hospital arrests have successful outcomes of only 14% and 16%, respectively (only 1 of 7 survive); (3) at least 80% of all patients experiencing cardiopulmonary arrests will have some residual brain damage; and (4) less than 25% of patients who experience cessation of cardiac electrical activity (systole) can be resuscitated (the expert’s personal experience and opinion was that it was closer to 5%). After this testimony, the jury rendered a verdict in favor of the defendant. The case was appealed, and the Delaware Supreme Court held that the admission of statistical evidence was erroneous, because its probative value was substantially outweighed by its prejudicial effect. In other words, the court said that the statistical probability of death or brain damage after a cardiac arrest cannot be used to show that a doctor did or did not act in conformity with the applicable standard of care, merely because the ultimate results were in line with the statistical probabilities presented. The Supreme Court stated:

It is settled law that the standard of care in a medical malpractice action is established by evidence of the degree of care and competence ordinarily exercised by physicians in the same or similar community. A defendant may not use evidence that a patient’s treatment ended with an expected result to infer the patient received proper care. If it were a fact that 80% of cardiac arrest victims die or suffer brain damage that fact is not relevant to the issue of whether [the defendant] deviated from the applicable standard of care in trying to resuscitate [the plaintiff].

The court noted that “statistical probability evidence creates a significant risk of jury confusion and unfair prejudice, because it might cause the jury to decide the case based on what happens normally instead of what happened in the [actual] case.” In essence, the court was trying to deal with the inappropriate association that, because a majority of patients who suffer cardiac arrest either die or suffer some neurological impairment, the plaintiff who happens to suffer a cardiac arrest is therefore expected to suffer death or brain damage. Rewording its message, the court stated: “Because such an inference is not based on the facts at hand, but rather an impermissible speculation based on inapplicable statistics, the potential for misleading the jury was quite substantial.”

Coming back to Pruitt , the court fashioned its own version of the established precedent by holding that, just as it is improper to use an unusual outcome to create an inference that the standard of care was breached, it is also improper to infer that a patient received proper care merely because the treatment outcome was what is normally seen in two thirds of all patients treated in that manner. For common behavior (results within statistical norms) to be admissible, the court noted that a special nexus must exist between that common behavior (statistically expected outcome) and the facts as established in the case at hand. Finding none, the appellate court reversed and ordered a new trial.