Charles Adams

Document Type


Publication Date



Nebraska Law Review


The doctrine of equivalents expands the scope of patent protection in some circumstances to cover variations of the invention that are not within the literal terms of the claims. While there is no statutory basis for the doctrine of equivalents, and it has been characterized as an anomaly, the Supreme Court has repeatedly reaffirmed the doctrine over the past 150 years. Although the Supreme Court and the lower federal courts continue to recognize the doctrine of equivalents, they have not clearly defined the circumstances in which it is available, nor demarcated the extent to which it expands the scope of patent protection. The consequent lack of certainty has adverse consequences for both patentees and their competitors because determining whether potentially competing products are infringing may require an expensive jury trial with the risk of damages and injunctive relief. A major source of this uncertainty is the fact that neither the Supreme Court nor the lower federal courts have articulated a convincing rationale for the doctrine of equivalents. This Article provides a critical analysis of the doctrine of equivalents. In Part II, the Article describes the evolution of American patent law from central claiming to peripheral claiming. Next, Part III discusses a statutory vestige of central claiming that is found in paragraph 6 of section 112 of title 35 of the United States Code for particular types of claims having a combination of elements. Part IV surveys the four leading Supreme Court cases addressing the doctrine of equivalents and discusses the limitations these cases have placed on the doctrine. Part V summarizes the current law and discusses future prospects for the doctrine of equivalents.