It's attitudes like this that allow goons with badges to get away with this kind of crap.
The elected city officials (read: mayor, city council) hold the cops' leashes.
The taxpayers elect the officials holding the cops' leashes.
If the taxpayers re-elect the officials without holding them personally responsible for cleaning up the dirty police, then the taxpayers should not complain about having to foot the bill when dirty goons with badges commit crimes.
Too many good taxpayers go back to sleep after casting their votes when they should be continually watching the elected officials to make sure the officials they elected are doing the taxpayers' bidding the way the taxpayers want it done.
It's really as simple as that.
IANAL, but I believe that the legal principle involved is *respondeat superior*:
http://legal-dictionary.thefreedictionary.com/Respondeat+superior
tl;dr: The taxpayers are on the hook.
There has to be a component of individual responsibility. I agree the City Leaders are ultimately responsible but there is already a law against planting evidence. If the cop doesn’t pay a criminal and civil penalty there is nothing to stop them.