I think that your points about biases in arrest and prosecution being more problematic than I considered are likely correct. I knew plea bargains were common,

I think that your points about biases in arrest and prosecution being more problematic than I considered are likely correct. I knew plea bargains were common, though the rate you cite is high but not implausible. If there is significant plea bargain rate disparity among racial/ethnic groups it might affect conclusions about impact of racial biases. While juries are not uniformly populated, in predominantly black communities I'd expect at least some jurors will be black. When there is a jury trial, a requirement for unanimous decision gives any juror "veto" power over a guilty verdict, which in principle mitigates racial bias against a black defendant. Many years ago when I lived in Washington, DC, blacks were by far the majority. In that environment, racial bias against black residents should logically be minimal in all phases of the criminal justice process. It's not the sort of question I've researched, but someone experienced in that domain should tackle it if the question is still unanswered. In any case, if bias is detected in such a community seems there's a serious problem of a different kind.