Talkleft points to a Jones v. Sterling, a decision of the Arizona Supreme Court regarding "Driving While Black." Since Talkleft is what I like to refer to "The Overlawyered of the Left" but the case is worth some discussion, I offer the following squib:
The defendants asked that the court approve the funding of an expert witness on racial profiling. The lower court held that racial profiling was not a substantive defense to the crime and Arizona's rules of criminal procedure specify that experts are to be paid only if "such a defense adequately at trial or sentencing". Arizona Rule of Criminal Procedure 15.9(a). The defendants sought what appears to be Arizona's equivalent of a writ of mandamus, and the Supreme Court concluded that although Whren v. United States, 517 U.S. 806 (1996) bars a appointment of an expert where the petitioners seek an expert to support an argument based on the “racial motivations“ of the officers, as Whren barred this as a defense, but Whren does not hold that selective enforcement is not a defense, and the defendants are entitled to an expert on the issue of whether the law was being applied selectively in violation of the 14th, but not the 4th amendment. The court then discussed when experts should be appointed.