Thediscriminatory purpose requirement established byWashington v. Davisposes significant challenges to suits alleging racial (or other) discrimination, even where there is a clear disparate impact. The Supreme Court has made these challenges even greater in recent years by tightening pleading standards, which, in effect, make it more difficult for plaintiffs to obtain discovery of precisely the information that could prove discriminatory purpose. Here's a short article discussing these developments. What, if any, lessons does this suggest about the relationship between constitutional rights and civil procedure.

http://worklaw.jotwell.com/plausibility-civil-rights-and-discovery/