Every day, countless civil lawsuits are filed in this country. Every day, countless plaintiffs seek relief from our nation’s court systems, whether it be to recover for economic losses, to prevent future illegal conduct or to challenge a law or regulation. For a lawsuit to continue past the preliminary stages, each plaintiff must allege some degree of facts and a cognizable legal theory that entitle that plaintiff to relief. In turn, each defendant has an opportunity to dispute the plaintiff’s factual and legal allegations and thereby contest the validity of the action. All of this is quite elementary to even the greenest of lawyers.

But now imagine a case where the plaintiff has an ulterior motive for filing his or her complaint: revenge for something else that transpired between the parties (this should require no great leap of the imagination). Can that ulterior motive be legally relevant to the action? And what happens when the defendant raises the issue?