I rarely refer to my military experience - it makes people make assumptions about me - but one thing here jumps out at me. Police sergeants in the US act like army sergeants!
Can it be that the problem lies with the idea of the police as a quasi- or para-military organisation, rather than a civilian one? A culture divided between the 'grunts' and the 'officers' with the NCOs standing between them?
As opposed to a Civil Service department where performance reviews are structured in a way that ensures that failure at the bottom is assumed to come from the top?