United States v. Adams
United States Supreme Court
383 U.S. 39 (1966)
Adams patented a water-activated battery using magnesium and cuprous chloride electrodes, and after the government initially deemed it unworkable before quietly adopting and using it without compensating Adams, the government defended the resulting infringement suit by arguing obviousness based on prior patents describing zinc and silver chloride batteries and separately suggesting magnesium or cuprous chloride substitutions, though none of those references suggested a successful water-activated magnesium system.
Whether, in determining if an invention is nonobvious, a relevant factor is whether, in creating the invention, the inventor ignored commonly accepted principles that naturally would have deterred an inventor from searching for new inventions.