Hotchkiss v. Greenwood

Hotchkiss (plaintiff) sued Greenwood (defendant) for infringing a patent on doorknobs made of clay or porcelain rather than the wood or metal used in prior doorknobs; the trial judge instructed the jury that if the only difference between Hotchkiss's doorknob and existing designs was that material substitution, with every other component already known in the art, the patent was invalid. Hotchkiss appealed, challenging that jury instruction.