The Festo decision posed a threat to the US doctrine of equivalents, or DOE. This doctrine has been relied upon for years by patent owners to stop copycat products that use technology similar to their original. Basically, the doctrine says that if a product or process is not substantially different from the elements of a patented invention, it is considered to be infringing.
Festo Corporation is a robotics company in Long Island, New York. It challenged a Japanese rival, Shoketsu Kinzoku Koygo Kabushiki, alleging patent infringement. The federal court ruled that there was no infringement. Significantly, it added that Festo lost certain rights in its technology as soon as it narrowed its original claim for a patent.
Until the Festo case, elements of an invention stripped from a patent claim during amendment were still considered the property of the inventor under US law, even if they did not appear in the formal patent description. The implications of this change in the law could be huge. Very few US patent applications succeed without some degree of amendment. Lawyers for some patent owners say that Festo has opened the door to copycat products. They also warn that it will add to the expense of securing and protecting a patent.
These arguments are disputed by some other patent lawyers. One opponent is patent lawyer Sean Johnston, quoted in business magazine Red Herring: “Is it really an invention in the first place if you don’t grasp the full scope of it, had to amend your claim, or use DOE to protect it? I don’t think so.”