@Frank Apisa,
My experiences with secret services are history as are those with police forces/prosecution etc (those more like "newer history") And more or less only related to the German situation.
But I do think that even today, if something really relevant would have been found, we would know it.
On the other side, it's often better to observe a bit longer - thus getting the real important behind it.
What has been stopped here in German was done be normal police work ... with some additional help from the (domestic) secret service.