Re: Stupid cops
The more cops around the world that became aware of this, the higher the chances that one of them would be bent and would leak, either to a criminal, or the press (or to someone 'in confidence', who then tells someone else, who talks about it in a pub, etc. etc.). Or eventually it would come out in court.
This was always going to be a limited opportunity to get as much evidence as possible before they had to reveal its source.