Lydia Basko (plaintiff) suffered from lupus erythematosus and, from 1953 to 1961, took three different drugs (Aralen, Atabrine, and Triquin) to treat it. These drugs were all manufactured by a division of Sterling Drug Co. (defendant). In 1956, a few years after taking the drugs, Basko experienced blurred vision. This condition continued to worsen, and Basko became almost completely blind. Basko brought suit against Sterling Drug as a result of these side effects, arguing that Sterling Drug failed to adequately warn her of possible side effects of the drugs. During the trial, Basko’s medical expert testified that her side effects were likely caused by drugs made from chloroquine, and Aralen and Triquin contain chloroquine ingredients. Prior to Basko’s use of these drugs, there had been reports of blurred vision in patients who took chloroquine, and Sterling Drug was aware of these reports when they occurred. However, Sterling Drug contended there was no evidence of retinal damage until 1957, after Basko began experiencing her symptoms. However, Basko took Triquin from 1959 to 1961. In 1962 Aralen and Triquin added warnings to its product card indicating retinal changes, although rare, could occur. The jury, on the issue of causation, was instructed to find for Basko if the jury determined one or more of the drugs caused her blindness. At the end of the trial, the jury found for Sterling Drug. Basko appealed.