Doctrine of equivalents

The doctrine of equivalents brings the need for delicate balance to the fore. As the U.S. Supreme Court recognized in its Festo opinion, the doctrine raises issues of claim transparency that affect the public:


 * This clarity [of patent boundaries] is essential to promote progress, because it enables

efficient investment in innovation. A patent holder should know what he owns, and the public should know what he does not.”

The doctrine of equivalents, however, “renders the scope of patents less certain. . . . If competitors cannot be certain about a patent’s extent, they may be deterred from engaging in legitimate manufactures outside its limits, or they may invest by mistake in competing products that the patent secures.” The Federal Circuit in Festo gave these considerations precedence, emphasizing the notice value of claims in finding a complete bar to application of the doctrine of equivalents to claim elements narrowed during the course of a prosecution. The Supreme Court ultimately softened the appellate court’s ruling, however, making the bar a matter of rebuttable presumption