We noted that a product may be defective if the manufacturer failed to warn the user of potential dangers. Whether a warning should have been affixed is often a question of what is reasonably foreseeable, and the failure to affix a warning will be treated as negligence. The manufacturer of a weed killer with poisonous ingredients is certainly acting negligently when it fails to warn the consumer that the contents are potentially lethal.
The law governing the necessity to warn and the adequacy of warnings is complex. What is reasonable turns on the degree to which a product is likely to be misused and, as the disturbing Laapericase (Failure to Warn ) illustrates, whether the hazard is obvious.