I have known several kids like that over the years (and, like many of us, have studied this personality type out of fascination). And enabling parents only magnify the problem (Joren Van der Sloot comes to mind).
The question is "how do you prevent their eventual crime without robbing the merely weird among us of their freedom to be weird?"
I think most kids and adults know the answer...stay the h$ll away from them.
The merely weird find other math and science nerds to hang with (;-D)...the true psychopaths are shunned by all but a few stupid saps (some of whom often end up as victims).
a history of violence, death threats is a red flag. The merely weird long haired kid who is oddly imaginative doesn't go around being violent or threatening others. Plus look at their origins. a criminal family versus an odd off beat family is a clue.