There’s not much to back this up, at least that you’ve included as reference.

The bigger issue that comes to mind and that you can actually look in to is the practice of teaching police departments about “Killology”. This is (or was) a kind of seminar that taught departments this mindset of “everyone that an officer interacts with is a potential threat”. Add this to the “super criminal” bs that was popular in the 80s/90s, the constant right-wing fearmongering about dangerous criminals in blue cities, and the militarization of police, and it feels more like they’ve been primed for violence from the power structure more-so than any actual threat from the public.

thats what happened to presumption of innocence absent indications of guilt.