Answer: Has a mental disorder
Explanation: The 4D's are: dysfunction, distress, deviance and danger.
Dysfunction is when a behavior causes disruption at a social level and troubles functioning in a day to day spectrum.
Distress is when a behavior causes yourself or your environment to feel unpleased or upset.
Deviance is when a behavior is not considered normal according to the frequency.
Danger is when a behavior can potentialy hurt yourself or others.
Taking into consideration what we know about Liam and this four D's, we can say that he qualifies as a person who has a mental disorder.