Couple of reasons. For starters, the guy is a former cop and has connections with the prosecutors. 2 DA's had to recuse themselves from the trial. I imagine that slowed the process some, though I'm not sure exactly how long that takes per instance. I think the only reason these guys weren't detained originally is due to the father's ties to the force, which is more of product of bureaucracy than systemic racism. The current DA seems to be taking the investigation seriously. There's virtually no way these dudes aren't indicted.

Fact check that information, because I'm doing it from memory. Hopefully don't have the details wrong.

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