As far as I can tell, ontologically, you're not a criminal until you get caught, just as a pressure wave (of a tree falling et all) is not a sound until it is observed by something with ears.
Experience of criminals being dumb? I'm not sure I understand why that would make me seem threatening. (I don't particularly mind seeming threatening, I just don't understand how saying criminals are dumb would make it so.)
That's not that hard. Criminals are notoriously really dumb. And lazy.