I don't see this as a question of confirmation bias but rather a more deeper problem in investigative law enforcement, namely the need to see things as part of a narrative relating to the sort of investigation. This isn't confirmation bias as usually understood, but goes one step before, namely in filtering out the details one can tell a story about.

In the end what criminal investigators do is they find details and piece together a narrative from those. One huge problem with massive surveillance is the ability to piece together whatever narrative the investigator wants to put together based on a much larger field of information to mine.