In the case of Bagley v. General Fire Extinguisher Company, 1908, the U.S Supreme Court was tasked with determining whether a patent for an invention could be invalidated due to prior use by another party. The plaintiff, Bagley, had patented a fire extinguisher design and subsequently sued the defendant company for infringement. However, it emerged that before Bagley filed his patent application in 1899, another inventor named Grinnell had used a similar design in 1883 but never patented it. The court ruled that under US law at the time (Revised Statutes §4886), if an invention has been "in public use or on sale" more than two years before applying for a patent then such application is voided - regardless of who made this public use or sale. Therefore since Grinnell's device was publicly used over two years prior to Bagley’s filing date; even though he did not apply for its own patent; this constituted sufficient grounds to invalidate Bagley's claim.

In the dissenting opinion for Bagley v. General Fire Extinguisher Company, it was argued that the plaintiff should not be barred from seeking damages due to a lack of explicit warning about potential dangers associated with using the fire extinguisher. The justice believed that there was an implied warranty by the defendant company regarding its safety and efficacy in use as intended. Furthermore, they contended that if a product is inherently dangerous or has potential risks when used normally, then it's incumbent upon manufacturers to provide adequate warnings regardless of whether such danger is common knowledge or not. They disagreed with majority's view on "common knowledge" defense stating this could lead to unjust outcomes where consumers are left unprotected against potentially harmful products just because some people might know about their inherent risks.