In the broadest terms, the impunity with which such a group could operate seems to be the problem we have in the United States, and which other nations confront as well.
I do have a question about the question posed though: Baldblog posits that this force acting with impunity includes:
people of varying ethnic and educational backgrounds and attitudesI'm left wondering whether having a police force that includes "various ethnic groups" is suggested as a potential risk factor for a force that acts with lawlessness and impunity. I'm not sure what "various ethnic groups" has to do with the premise. Likewise, I'm not sure that various "educational levels" is a significant part of the problem. Medical doctors, who have more education that most people in our society, nonetheless have been proved to provide less agressive and less appropriate medical care for members of minority groups (and women) than they provide to white men, in spite of the fact that doctors have immense education, particularly in the area where they seem to discriminate against minorities and women.
If Bradblog is reading, maybe he can discuss the issues of people of "varying ethnic"backgrounds and "educational backgrounds" as risk factors for police lawlessness and impunity. For example, would an all-white police force be more accountable than a multi-ethnic force. It seems that "attitude" is more important than ethnic composition and educational level, although the existence of an all-white police force can be an indication, by itself, of the "attitude" of those selection and supervising the police.
I believe the problem is not "ethnic backgrounds" or "educational levels" but rather the third factor that Bradblog mentioned: "attitudes." An attitude, literally, is a tendency to go in one direction or another. When voters go to the polls, for example, skin color can often be helpful in predicting how they will vote. However, it seems to me that police officers' attitude is influenced more by the role they have in society (control the populace) which may even require that they demonstrate that they can act with impunity and irrationality. When an occupying force can act this way, with no negative consequences, it demonstrates and reiterates its control over the target population.
Perhaps part of the functional purpose of irrational acts of impunity is to demonstrate to the population the unquestioned authority of the police, who effectively say, 'You are powerless in your interactions with us and in our control over you.'
Does everyone agree?
Baldblog's posts also point out the difficulty of establishing police review boards (CRB's) and pose the question of whether any of them are actually able to do anything worthwhile?