Court Clarifies Patent Boundaries. (Perspectives: News and Views of the Current Research * Technology Management Scene) (2002)

The Supreme Court of the United States has again changed the rules of patent claim interpretation in an important decision handed down on May 28. Its ruling in the Festo vs. Shoketsu Kinzoku Kogyo Kabushiki Co., Case 00-1543, rejects a lower court ruling which severely limited application of the doctrine of equivalents, but restores just some of the benefits of this doctrine to the inventor. Technology managers should understand the nuances and implications of this ruling for two reasons: 1) so that their organizations' inventions can best be protected and 2) so that they can understand the territories covered by competitive patents. The doctrine of equivalents grants protection to the spirit of an invention beyond the literal language of its claims. It prevents me-too copiers from using other peoples' inventions by making small changes. The issue in these cases has been what should be the allowable zone of equivalence for patent claims that have been amended during patent prosecution. Patent prosecution is the back-and-forth process of Patent Office actions and replies that usually goes on between the patent filer and the Patent Office before a patent is granted. The state of the law before the November 29, 2000 Festo decision was that, if a claim was amended to narrow its scope, a flexible bar was created to asserting any coverage beyond the literal language of the amended claim. Courts would have to decide controversies on a case-by-case basis, depending on the background and reasons for amending. For example, let's look at a claim that originally said less than 20, and after the Patent Office rejected it based on prior art that disclosed a value of 15, was amended to a value of less than 5. There was no sure way that another inventor could use a value of 5.5 or 10 or 14 with confidence. This gray area would remain uncertain unless litigation settled the matter. The November 29, 2000 decision of the lower court said that any territory above 5 was given up by the inventor when he amended his claim, hence no equivalent coverage. Further, the court held that this territory would be gone even if the amendment was not made to avoid prior art. In effect, it ruled that amending a patent claim created an bar to asserting the doctrine of equivalents. This had the virtue of eliminating much of the gray area in interpreting patent claims. The Supreme Court decided that the absolute bar ruling went too far but recognized the need for clarifying the scope of doctrine of equivalents for amended claims. The new standard the Court has promulgated is being called a foreseeable bar. Basically, it says that, when you amend a claim to make it narrower, you can no longer claim the territory you gave up as part of your zone of equivalence. You will, however, still have doctrine of equivalents protection for alternatives which were not claimed at the time because they were unforeseeable. Let's say you had patented a device incorporating vacuum tubes as an element of the invention. When transistors were subsequently invented, parties would not be able to get around your patent by substituting them for the vacuum tube. …