With the D.C. crime rate spiralling completely out of control in light of their stringent gun control schemes, the people turn to a somewhat Orwellian solution:
People think that justice means sacrificing liberties. This is because methods of preventing crime appear to restrict liberties by polarising power in favour of the police, for instance a city wall with a policeman to check ID cards at checkpoints. However at the heart of a libertarian justice system is the people, 3 states of mind that exist in people.
1: Professional police, people who legitimately believe in the various dogmas that inspire responsibility and recognition of their role in society. When they are not under the constant eye of other police and the public they don't think to themselves that this is an opportunity to do whatever they want.
2: Assholes, people who police professionally purely so they get a pay check and don't arouse suspicion, but when left to their own initiative act in their own shallow interests.
3: Machiavellis, similiar to an asshole except with the ability to put aside quick gains for long term goals, these 3 states of mind are malleable, commonly a professional policeman will turn machiavelli convinced by some stimuli to achieve a wider political goal or avoid having pictures of him sucking a little boy's dick sent to his wife.
There will always be people with these 3 states of mind in the police, I'm sure you can think of many measures to take this into account. My point is that it is ok to give the police power as long as you have analysed whether it is possible for the police to abuse that power.
If the police is heavily infiltrated by the local population who have families and friends in the local area, there are dozens of senior ranking police lieutenants and none of them has any power beyond that of an ordinary police men and merely act as mentors and figureheads for planning the most efficient method of policing and dealing with various problems. Chances are there will be assholes and machiavellis in this wonderful police department, but since whatever assholes and machiavellis there are are know they are probably alone, there is little they can do that won't arouse suspicion and may well change their minds after their work becomes part of their life this police force would be well capable of not abusing their power if say a wall was built around the town and security cameras placed to view al public property.