Regarding the question of who watches the watchers, I do wonder if any country has tried appointing a group of citizens who essentially get to watch everything

Regarding the question of who watches the watchers, I do wonder if any country has tried appointing a group of citizens who essentially get to watch everything the police do. It would seem like that primary complaints would be that the officers privacy is violated and secondly that people who are under investigation’s privacy would also be violated. But otherwise what kind of oversight or threat of oversight do these guys have? Maybe another approach is you have a group of pseudo officers that are like internal affairs people who’s job it is to investigate the police and maybe that could extend to “watching the watchers”?