Well a confession is a pretty specific area—it always takes place in a confessional between two people. What evidence is acceptable to you that one of these two people heard something from the other and then broke the law? A recording? A simple claim? Or what? Seems like you could fill me in if you know how it will work.
Freegards
It isn’t as though the nature of evidence were up to me to decide. It is up to individual jurisdictions to decide. Look to existing legislation. In the US, warrants and judicial hearings would be involved but I have little knowledge of how they do things in Australia.
God raises up civil governments because when we each do that which is right in our own eyes we mess things up. Even clergy, regarding some things.