True, but no DA can press charges if he doesn't have adequate information from the police with regards to what happened. If the cops didn't arrest anyone, make any reports, take down notes, etc. then there's nothing for the DA to work with.
Unions will always protect their own. That's why nearly all unions can get away with committing as many acts of violence as they damn well please. They know the cops have their backs.
FWIW, that can and does happen, especially if there's a question about LE's conduct during an investigation. The DA's office can conduct its own investigation.
I'm recalling the Don Adams incident from years back, and it's my impression that some judges are also DEM hacks, who will deny damages to a conservative complainant in a civil suit, when the defendant is union or DEM, etc.
I'm of the firm opinion that, other than contract and some routine family law matters, our justice system fails to meet the standards for objectivity and adherence to the constitution.