Na the police play it like this to get the suspect to slip up.
They have done it a few times in the past where they have most evidence but need a slam dunk. The Jetstar pilot involved in the elderly couple camping remote for example.
They tell them they are not looking at them (but bug their house / car etc), then leak stuff to the media to spook them into talking or trying to hide evidence.
A few months later the police have already filled out all the paperwork for a slam dunk and make the arrest.