In the 1936 case of Essex Razor Blade Corp. v. Gillette Safety Razor Co., the U.S Supreme Court dealt with a patent dispute between two razor blade manufacturers. The plaintiff, Essex, accused Gillette of infringing on its patented design for a new type of safety razor blade. However, Gillette argued that their product did not violate any patents as it was based on an expired patent and therefore in public domain. The court ruled in favor of Gillette stating that once a patent has expired, anyone is free to use the invention or design without fear of infringement claims from the original holder or those who have obtained rights under them during life time of such patents. This ruling reinforced one key principle underlying US Patent Law: Patents are granted to encourage innovation by giving inventors exclusive rights over their inventions for limited period; after which they become part of public domain available freely for everyone's benefit.

The dissenting opinion in the case of Essex Razor Blade Corp. v. Gillette Safety Razor Co., argued that the majority's decision to uphold a patent infringement claim was incorrect, as it failed to consider whether or not there was any actual novelty in the patented design. The dissent emphasized that patents should only be granted for truly novel and non-obvious inventions, rather than slight modifications or improvements on existing designs which do not significantly enhance their utility or function. In this particular case, they believed that Gillette’s patent did not meet these criteria because its razor blade design closely resembled prior art and thus lacked sufficient novelty to warrant protection under patent law.