No police union contract includes a statement that the officers are immune from criminal investigation and prosecution, and most of the egregious events would clearly result in investigation and prosecution (if not necessarily conviction) if done by non-police. That these cases don't get that far shows the effects of a general cooperation between police and the judicial and political system---DAs don't prosecute and courts won't convict---all backed by a social system that encourages that behavior: you won't get elected on a police reform platform anywhere in the US.
No police union contract includes a statement that the officers are immune from criminal investigation and prosecution, and most of the egregious events would clearly result in investigation and prosecution (if not necessarily conviction) if done by non-police. That these cases don't get that far shows the effects of a general cooperation between police and the judicial and political system---DAs don't prosecute and courts won't convict---all backed by a social system that encourages that behavior: you won't get elected on a police reform platform anywhere in the US.