I recently had the chance to talk with a veteran defense attorney who has represented a number of cases. We were talking about a client who was up for a charge, and the attorney observed that if you want to get away with ing someone, you need to do two things. In his words and my elaboration:
1) "Kill an asshole." Part of what happens to accused criminals depends on who they have harmed. Want to get off lightly? Kill someone that nobody cares about or that people don't like. E.g., a dealer rather than a pediatrician. This highlights the extra-legal factors that come into play in criminal proceedings. It also brings in social values about who is valuable and who is not, who is worth protecting and who is not. Not all victims are equal.
2) "Don't talk to the police." In many criminal cases, the words of the defendant are the most powerful evidence that the state has in convicting them. Ironically, talking is optional, and the police even tell defendants that they don't need to, and it can be used against them.
Clear, compelling evidence? Equal treatment to all? Probably not in this system.