Originally Posted by Darth Rotor
If that's addressed to me, then I'm not sure where you got that impression from. I made no assumption about there being a single principle, what I actually asked was: "What are the principles that American policing is founded on?", which was intended as an open-ended request for information. Yes, I could go and google for it, but I know there are members here with first- and second-hand experience of law enforcement in the US who could give a more reliable account. (In fact, I did google, and did find reference to Peel's principles from some of the bigger US police forces, but that didn't say that they were actually the basis for policing rather than a comparison.) I know a couple of people who have been in the police in the UK, and from them I get the feeling that while adherence to the principles may vary over time, they are always there for reference, something to be returned to when practice drifts too far away from the ideal.
If, as you seem to be suggesting, each local force makes up its own principles, or even does without, then it's not surprising there may be large variations in how they go about their task, even leaving variations in the requirements locally.
FWIW, we don't have a national police force in the UK, either.