Hi Ralph,
I don't know what level you are writing this piece at - though there are some fascinating works on police and police culture. Two that stand out for me are an ethnography by John Van Maanen (at MIT, I believe) where amongst many other things relevant to your study he describes his fears of being bitten by a police dog or shot by police as he does his fieldwork. The other is a fairly high level dissertation done by a Fielding graduate named Kathy Long who developed a systems theory of how the police, justice system and the community interact. Its called "When Demons dance" and I guess will be available thru UMI. She points out the difference or the "line" between crook and cop can become very thin indeed.
Good luck - its a fascinating subject