Steve Osborne: The Job: True Tales from the Life of a New York City Cop

I always liked working in plainclothes. What we did was, especially in Manhattan, we would drive around [in] a yellow taxicab, which was actually a police car, it was identical to all the other 13, 14,000 taxicabs that are out there, you couldn't tell the difference just by looking at it. We would use that to go out and follow guys. ... Our job was to go out, blend in the crowds, and look for the bad guys before they did their crime.
-Steve Osborne

You really got about one second to make a life-and-death decision.
-Steve Osborne, The Job: True Tales from the Life of a New York City Cop by Steve Osborne

http://www.npr.org/2015/04/21/401238481/after-20-years-on-the-job-nyc-police-officer-tells-his-intense-stories