if you're not familiar, look up what they did with cointelpro during the civil rights movement. some of it is so wild. look up Jean Seberg. i can't say with any surety that that sort of thing is /better/ regulated in the present. i think it'd be safe to assume the opposite.
shout out afeni shakur, who while on trial AND doing her own legal defense, proved the state had infiltrated the black panthers and were also the main source of plans for violent attacks that led to her (and others) arrest. Also SpyCops in uk being real and no formal resolution
that story is always so amazing. i don't know about SpyCops, i'll have to read up on that!
You could just listen..
i dont have any book/source references but most investigations into the Special Branch are worth checking out. Lots of extrajudicial murder, colluding with paramilitaries, etc.
It's certainly much easier to do online.