Here's HOW it works, the 4th Amendment's strictures against "unlawful search and seizure" DOES NOT apply to public surveillance.
Because there's no reasonable expectation of privacy in a public space.
I support Body Cams for police...and actually for all Emergency Responders. I support them in the certainty that in about 98+% of all interactions, the police will be vindicated.
A civilian has no right to confront/challenge and arrest, even when the civilian believes that arrest to be "false," "malicious," or otherwise "unlawful."
Because (1) Police are legally allowed to arrest based solely on suspicion and (2) the civilian rarely has a full understanding of the law. At any rate, the Courts are the ONLY venue a civilian has to challenge an arrest.
As far as the existing and expanding surveillance state goes, NONE of us has any reasonable expectation of privacy in a public place. Cameras are ubiquitous...and that’s proven to be VERY good, making it much harder for street thugs to get away with street crimes.
Like DNA technology, Police Body Cams will vindicate a few civilians (and bad cops deserve no more "privacy" than a thug does), but those technologies will make the prosecution of far more criminals much, MUCH easier.
That, despite the ACLU's misguided complaints a VERY good thing!
Why is the ACLU Afraid of Body Cams?