The biggest hurdle is the blue wall of silence.

[Bluenorthwest]

11. The Police Are Still Out of Control I should know. By Frank Serpico October 23, 2014

"I still get hate mail from active and retired police officers. A couple of years ago after the death of David Durk — the police officer who was one of my few allies inside the department in my efforts to expose graft — the Internet message board “NYPD Rant” featured some choice messages directed at me. “Join your mentor, Rat scum!” said one. An ex-con recently related to me that a precinct captain had once said to him, “If it wasn’t for that fuckin’ Serpico, I coulda been a millionaire today.” My informer went on to say, “Frank, you don’t seem to understand, they had a well-oiled money making machine going and you came along and threw a handful of sand in the gears.”
http://www.politico.com/magazine/story/2014/10/the-police-are-still-out-of-control-112160



Serpico: I'd fire the NYPD officers who turned their backs on the mayor
In his first TV interview in years, the legendary whistleblower speaks out about today's police controversies
January 15, 2015
http://america.aljazeera.com/watch/shows/america-tonight/articles/2015/1/15/serpico-i-d-firethenypdofficerswhoturnedtheirbacksonthemayor.html