In the 1938 case of Electrical Fittings Corp. et al. v. Thomas & Betts Co. et al., the U.S Supreme Court dealt with a patent dispute between two companies over an electrical conduit fitting design, which was patented by Thomas & Betts Company (T&B). The plaintiff, Electrical Fittings Corporation (EFC), alleged that T&B's patent was invalid due to prior use and sale of similar designs before the patent application date, thus violating novelty requirements under U.S Patent Law. The court ruled in favor of T&B stating that EFC failed to provide sufficient evidence proving prior use or sale beyond reasonable doubt - a burden placed on those challenging validity of patents as per established legal principles at that time. Furthermore, it held that minor differences between earlier designs and T&B’s patented design were enough to establish novelty for granting patents; thereby rejecting EFC's argument about lack of inventiveness in T&B’s design.

The dissenting opinion in the case of Electrical Fittings Corp. et al. v. Thomas & Betts Co. et al., argued that the majority's decision to uphold a patent on an electrical conduit fitting was incorrect, as it did not meet the requirements for novelty and non-obviousness necessary for patent protection under U.S law at that time (1938). The dissent believed that prior art existed which showed similar designs and functionality, thus negating any claim to originality or inventiveness by Thomas & Betts Co.. Furthermore, they contended that even if there were slight differences between this design and previous ones, these alterations would have been obvious to anyone skilled in the field of electrical fittings manufacture; therefore failing another key test for patentability - non-obviousness.