Jason Bull is devastated when they win their case and his psychotic friend walks free on Bull. "Grey Areas" is the 12th episode of the show's second season.
Thoughts and actions are two different things. That's why the professional standard in a case like this is for the psychologist to determine if there is a serious and imminent threat.
Psychologists aren't mind police. Holding them responsible for the actions of their patients after they leave the doctor's office is not only impossible, it's dangerous.