In a sense, the causal link requirement and “the but for” requirement are two different but related ways of asking whether a defendant's actions were a substantial factor in causing the injury. Causal link says that, even if defendant's wrong was a “but for” cause of the injury in a given case, no liability ensues unless defendant's wrong increases the chances of such harm occurring in general. “But for” says even if what the defendant did greatly increased the risk of certain injuries occurring, unless it was a sine qua non (essential condition) of the specific harm that actually came about, no liability is assessed.
Mrs. Zuchowicz filled a prescription for the drug Danocrine at the Naval Hospital pharmacy in Groton, Connecticut. The prescription erroneously instructed her to take 1600 milligrams of Danocrine per day, or twice the maximum recommended dosage. While taking Danocrine she experienced abnormal weight gain, bloating, edema, hot flashes, night sweats, a racing heart, chest pains, dizziness, headaches, acne, and fatigue. On May 30, she was examined by an obstetrician/gynecologist in private practice who told her to stop taking the Danocrine. In October 1989, she was diagnosed with primary pulmonary hypertension ("PPH"). The spouses filed a negligence complaint against defendant. Plaintiff relied on the expert opinions of a pharmacology professor and a pulmonary disease expert. The lower court held defendant's negligence caused plaintiff's wife's PPH and awarded damages to plaintiff. Defendant appealed.
Whether sufficient evidence was presented that the overdose prescription of Danocrine caused Mrs. Zuchowics' death?
The court held that the basis of expert testimony alone, the finder of fact could have concluded that Mrs. Zuchowicz's PPH was, more likely than not, caused by Danocrine. While it was not possible to eliminate all other possible causes of pulmonary hypertension, the evidence presented showed that the experts had not only excluded all causes of secondary pulmonary hypertension, but had also ruled out all the previously known drug-related causes of PPH. In addition, based on the expert testimony the progression and timing of Mrs. Zuchowicz's illness in relationship to the timing of her overdose supported a finding of drug-induced PPH to a reasonable medical certainty.