The only way to catch these people is to play them at their own game.
False CV's False email addresses and send them screenshots of a large bank account to wet their appetite and then get them to meet you.
Hopefully the greed for the money will convince them to break trend and come out in the open.
Other steps to make sure is get them to send an email from an account that is not web based like gmail then you can track them to their location.
There are also other ways but main thing is give it to them as hard as they give it you ....