You might mix privacy with authority responsibility and transparency. Cop, even bad one have two states - ordinary citizen and cop. Cop when he is cop is not a regular person - he is doing specific job that was given to him by people who hired him and paying him salary for doing that job. So when cop is a cop, his employer AKA people, have full and unlimited right to control and monitor his every single move. Especially taking in account specific rights people grant to cops.

What you might want is something like that - when he is cop, his every single step has to be documented videoed, recorded and should be publicly available. People pay his salary and have full right to check how he do his job. When he is a citizen he have full rights for the privacy as anybody else and no any cop privileges and rights. If his actions as a cop is (was) not documented for whatever reason (mY cAmErA wAs bRoKeN!!!), he is (was) not a cop at that moment and have no any privileges or cop rights at all. So, cop doing something wrong he want to hide, had to turn off his recording device, and at that moment he became just a criminal and victim could do anything for defence without any consequences.

Society have a full right to control and monitor any state or government official without any limitations. Since that is society hired them and pay them salary.

All above, of course is for some better society, not for current one.