Depends on the severity of the act. Shunning is excellent punishment for low-level misbehavior. If you allow misbehavior to accrue and expand, eventually you'll get to a case where you need a prosecutor.
That prosecutor's job would be easier if the criminal officer's colleagues would testify against them, which goes back (again) to social mores.
Prosecutors rely on cops to get their prosecutions, and if the prosecutor is the only one who faces repercussions for charging a cop, then obviously they're going to be loathe to charge any cops.
Honestly, though, the system isn't recoverable in most regions. American police, the ideological successors to slave catchers, suffer a rot that is too deep. Many are literally white supremacist gangs. It isn't a system that can be reformed.
That prosecutor's job would be easier if the criminal officer's colleagues would testify against them, which goes back (again) to social mores.
Prosecutors rely on cops to get their prosecutions, and if the prosecutor is the only one who faces repercussions for charging a cop, then obviously they're going to be loathe to charge any cops.
Honestly, though, the system isn't recoverable in most regions. American police, the ideological successors to slave catchers, suffer a rot that is too deep. Many are literally white supremacist gangs. It isn't a system that can be reformed.