A men was sentenced to prison for faking mental retardation and accepting disability payments. What busted him? He didn't behave as if he was developmentally disabled when he went to court for a traffic violation.
The article mentions that he began receiving benefits when he was 8 years old. There must have been something going on with him to receive benefits at that age, because it's highly unlikely an 8-year-old would be sophisticated enough to keep up such a ruse for years.