Part of the injustice system involves the DAs, judges, and governors (something that needs to be a higher priority for voters). If they decide not to press charges at all, apply lesser charges, or convict without applying the maximum penalties - all that sends a message. One of the worst examples was the killing of Ahmaud Arbery, in which there were coverups and connections between the perpetrators and members of the law enforcement community. Cases where the evidence is deliberately hidden or released years later is another ongoing issue.
A top to bottom scan of the cases highlighted in the Black Lives Matter Still and Defund the Police? topics might shed some light on the difference community pressure, civil suits, and escalation to federal authorities can make in combatting this fuckery. So far, the few rare cases when LEOs admit to a problem quickly tend to involve throwing POC and women under the bus. 
Yup. I thought Beau’s comments on the DOJs recommendations for Louisville were interesting:
