It's for the criminals...   So let's imagine 1000 people standing In a stadium.  100 of those people committed a crime. 10 committed a felony of great seriousness but a single 1 commuted genocide, child rape, cannibalism. Etc.  You know of the 1 Uber-criminal and dont care about the 100 much.  It's the 10 you want to figure out.  How to do it.  Well you start to talk about potential crimes...   You build a gallows at one end of the field.  Many go over and look at...  Some won't go near it though.  Then you toss out leaflets showing some potential crimes!    Some of the people Cheer but some recoil in horror.  See my point?  Do this enough and you can find every single one based on their reactions and actions, Now you can't use that data to convict them but you CAN use it to identify who to investigate.  My guess is what we are seeing is a way to fast-forward an investigation that would take 500 years with normal methods.  All the criminals self-identify.  I'm just a stupid redneck though so what do I know.