They only put the cop at the right place and at the right time, because they chose the place and time ahead of time.

You will never have information that's so secret that you can't build a parallel construction, because you always create a parallel construction that gives the appearance of random chance. "Well, your honor, we decided to setup a traffic safety roadblock stopping every blue car, and when the defendants stopped they started acting suspicious, and then it just happened that a k9 unit that was returning from delivering coffee alerted on the car. At which I point I searched the car and found the evidence. Somedays, we just get lucky."