Judging books by their cover

Why do murderers, sick perverts and rapists always look dodgy? Anyone strange looking should be locked up before they can commit crimes - I suppose Chelsea would have to find a new manager if that happened. *

* for legal reasons, I must say that Avram Grant is neither a murderer, pervert or rapist. Hopefully he will be a league champion in a few weeks time (at the expense of Man Utd)