A review of the literature reveals that there is little evidence for racial bias in the US justice system as a whole, though there likely is bias in some local jurisdictions:

http://slatestarcodex.com/2014/11/25/race-and-justice-much-m...

I was as surprised as you likely will be. The exception is with capital punishment. It looks like black people are more likely to get it than others. But otherwise nationwide crime and punishment statistics look mostly fair.