For the most part I do trust the police. Figuring that only a few of the hundreds of thousands of police make the headlines, and knowing that most police are aware of their mission to protect and serve, I would trust the majority of them to do what is right and what their job calls for.
There is a trend of militarizing the police force and apparently their mission, however, that if it continues, may cause me to reconsider my position on how much good versus bad they accomplish.