Diseases - Some brain diseases have been linked with criminal or anti-social behaviour. For example, in the 1920s, epidemics of encephalitis lethargica among children were linked to destructiveness, impulsiveness, arson and abnormal sexual behaviour. Other brain diseases, including senile dementia, Huntington's chorea and brain tumours have also been linked to various forms of deviant or anti-social behaviour.
Abnormal brainwave activity; Brainwave activity is measured by an Electroencephalograph (EEG). Some studies show abnormal EEG readings among 'clearly insane' murderers and psychotic criminals.