As usual, the real situation regarding convictions is disguised.  These day's DA's grossly overcharge in order to force "perps" to plead guilty to a reduced set of charges.  It is not that a jury rendered the decision.  Social, economic, and educational factors may force blacks or other minorities to accept plea deals and thus they show up as "convicted."  Since the plea bargain process is totally controlled by the DA's office, the high "conviction" rate may represent even worst overcharging of minorities by the biased DA.