This Comment empirically investigates the doctrine of inequitable conduct in patent law. Inequitable conduct is a defense to patent infringement that accuses the patent holder of committing fraud on the U.S. Patent and Trademark Office to secure the patent. Before the Federal Circuit’s recent Exergen and Therasense decisions, the defense was seen as chronically overused. As a result, patent applicants cited more prior art in their applications to avoid later being charged, during litigation with fraudulent omissions. The Federal Circuit responded with Exergen and Therasense, which heightened the pleading standard and raised the legal proof required for inequitable conduct, respectively.

Many commentators, and especially members of the patent defense bar, now feel that the Federal Circuit has gone too far in restricting the inequitable conduct defense, to the point that it is essentially a dead doctrine. This Comment informs the debate by adding comprehensive data. To better comprehend the effects of the Exergen and Therasense cases, this Comment calculates the rates at which accused infringers plead and prove inequitable conduct—for every patent case over the periods in question. The results show that the inequitable conduct defense is used significantly less often than many assume, contradicting assertions by the Federal Circuit’s Therasense majority. Moreover, the data indicate that Exergen and Therasense have both contributed to an even further decline in accused infringers’ use of the inequitable conduct defense. Based on a full exploration of the data, the Comment concludes that the Federal Circuit went too far in Therasense (but not in Exergen). A better formulation of inequitable conduct doctrine would be the test advocated by the dissent in Therasense, which embraced the U.S. Patent and Trademark Office’s lower standard of materiality.