ABSTRACT
Second, there does not appear to be any fixed and identifiable XYY syndrome, which means the concept is not useful in predicting criminal behaviour. Third, the offending behaviour of some young males with an extra X chromosome may be due to anxiety in adolescence about an apparent lack of masculinity. Fourth, all the young male offenders with an identified extra Y chromosome have come from working class backgrounds. It is thus possible that because young males with an extra Y chromosome are usually tall and well built, they may be defined as ‘dangerous’ by judges and psychiatrists, and more likely to be incarcerated than fined. Finally, and crucially, there are thousands of perfectly, normal and harmless people in the general population who have either an extra X or Y chromosome.
