Responding to views from the United States Patent and Trademark Office (“PTO”) and elsewhere about the unintended consequences of the inequitable conduct doctrine in its current form, the Federal Circuit issued a divided en banc ruling yesterday that will make it harder to establish the requisite showings of materiality and intent to prevail on this defense. Writing for the majority in Therasense, Inc. v. Becton, Dickinson and Co., Chief Judge Rader emphasized the impact of a finding inequitable conduct (unenforceability of the entire patent) and lamented that the doctrine has been overused to the detriment of the courts and “the entire patent system.”

Inequitable conduct is an equitable defense to patent infringement that, if proved, bars enforcement of a patent. This judge-made doctrine evolved from a trio of Supreme Court cases applying the equitable doctrine of unclean hands.