Re: Bias in, bias out
The fact that a certain postcode has an elevated amount of crime may not tell you very much about the perpetrators, merely, say, that the neighbourhood has a bunch of easily-nickable cars on driveways. If the crime is, say, burglary, the chances are the police are going to ignore it anyway.
If all crime were treated equally, then its distribution would be usefully informative. When you start to make choices about which crimes to pursue, then the information may simply reinforce any unconscious bias in your original choices to the point if becomes Kafkaesque.