How would you know if someone has antisocial behavior disorder?

Disregard for others: I'm wondering if you mean antisocial personality disorder. If a person has this, they would show a long standing pattern of anti-social attitudes and behaviors, including some of these: 1) lack of guilt, remorse, and care towards others; 2) minimal consideration of social norms and rules; 3) few close relationships; 4) trouble dealing with frustration and anger; and 5) a tendency to blame others.

Antisocial: The hallmark of this disorder is the person seems to have no conscience, or sense of morality, or right or wrong. This person cannot empathize with others, is opportunistic, predatory, and often thrill seeking. An example of this would be Charles Manson.