As YeZ points out in this answer, "daat" is the Knowledge of Good and Evil. Do sociopaths and/or psychopaths lack the דעת of the distinction between good and evil?
Traditionally the answer to this question is ein adam choteh ela im kein nichnas bo ruach shtus, a person does not sin unless a spirit of insanity has entered him.
So the question is, he should always be patur?
And the answer is he is chayav for letting the ruach shtus enter him and the consequences thereof.
But if the person is deranged this logic is inapplicable.
Virtually the whole of 'Rational Irrational Man' addresses this question.