What is the after-acquired evidence defence in the context of a wrongful termination claim?

When an employer being sued for wrongful termination learns after the fact that the plaintiff-employee committed misconduct which would have led to the termination in any event, that knowledge is called after-acquired evidence. (Murillo v. Rite Stuff Foods, Inc. (1998) 65 Cal.App.4th 833, 842 (Murillo).) The doctrine provides for an equitable defense related to the concept of "unclean hands." (Thompson v. Tracor Flight Systems, Inc. (2001) 86 Cal.App.4th 1156, 1173.)