Employers are not permitted to create requirements for jobs that have a disparate impact upon the ethnic composition of the workforce, if such requirements are not necessary for the job. But "once a plaintiff has established a prima facie case of disparate impact, the employer may defend by demonstrating that its policy or practice is job related for the position in question and consistent with business necessity." Furthermore, "the City's assertions that the exams at issue were not job related and consistent with business necessity are blatantly contradicted...

DeStefano. University of Cornell Law School. 2009. January 2, 2010
http://www.law.cornell.edu/supct/html/07-1428.ZS.html