By Francis C. Lynch ( July 6, 2018, 1:04 PM EDT) -- The Federal Circuit recently held that unclean hands based on serious business and litigation misconduct barred Merck & Co. from enforcing two patents against Gilead Sciences Inc.[1] This article describes the Gilead court's reliance on the U.S. Supreme Court's flexible framework for analyzing patent-related misconduct and its connection to the patent's enforcement under the unclean hands defense; and compares that framework to the defense of inequitable conduct used by the Federal Circuit to analyze misconduct in the patenting process. The article then explains why the unclean hands defense (1) always should be considered when there is clear evidence that the patentee has engaged in serious misconduct in the possession or enforcement of patent rights (other than in the patenting process) which can be connected to the enforcement litigation in a meaningful way; and (2) also should be considered when the patentee has engaged in serious misconduct in the patenting process by failing to disclose prior art information and that conduct also can be connected to issues in the enforcement litigation but not in the outcome-determinative way required under the Federal Circuit's inequitable conduct defense....