They tend to be officers who have policed an area for a long time, so they have that background. They tend to be at the end of their careers. Again, in every case I have ever done involving organized crime, that's the first dispute with the police--in terms of who their expert is and what they know about the group. It comes down to what the superintendent said: it's simply the training and resources.
You can do it for only a brief window of time and then you become stale-dated because you're away from policing it. The difficulty is that you constantly need them.