Since this particular type of claim is often litigated in the pharmaceutical context, I will provide a typical example. Pharmaceutical company P manufactures a drug which it has reason to know can cause the negative side effect of excessive bleeding in pregnant women, but fails to disclose it to consumers in its warnings. Woman W, who is pregnant, and is particularly concerned about vaginal bleeding due to her particular medical history, suffers hemorrhaging which requires corrective emergency surgery as a direct result of taking this drug. Had W known that P’s drug has this possible side effect, she would have used the comparable drug manufactured by C, which does not have this side effect.
In order to prevail on this theory, the plaintiff will have to prove that if adequate warnings had been provided, the injury would not have occurred.
Importantly, and as a practical matter, this burden is often difficult to meet, because the defenses to this claim are typically quite formidable. In particular, defendants often rely on their apparent compliance with labeling requirements promulgated by the relevant overseeing body (such as the FDA) as proof that they acted properly. Therefore, even where they believe that they have a viable failure to warn claim, plaintiffs will almost always claim at least one more of the other 5 bases for bringing a defective products lawsuit.