Just because a person is not expressive (or is introverted) does not mean
they have little or no empathy. These types show their concern by generous
behaviors, but may be uncomfortable verbally.

I have a book called The Sociopath Next Door. In it are estimates that 1 in 25 are sociopaths.

For you Mel, I've seen articles about autism and Asperger's and these patients may resemble criminal psychopathy, but typically are NOT criminal.
So lack of empathy is not always a sign of criminality. Criminal behavior is also connected with lack of conscience. And I think those are two separate issues.
Lack of conscience seems to be genetic.

But I agree you must endure alot with your son. I would find it very hard myself to deal with that level of lack of emotion. I guess that is why many Asperger's patients live alone.