In pari delicto is an equitable defense asserted when a defendant claims that a plaintiff is equally at fault for the wrong that has befallen him. The doctrine is “rooted in the common-law notion that a plaintiff’s recovery may be barred by his own wrongful conduct.” Pinter v. Dahl, 486 U.S. 622, 632 (1988) (citing Bateman Eichler, Hill Richards, Inc. v. Berner, 472 U.S. 299, 306 (1985)).