Evoked event related potentials are, nowadays, an important technique to use when we have to distinguish a high risk for psychosis (CHR) from psychotic disorders (PS) or from healthy subjects. This is an important tool also in penal process when neuropsychologist has to determine if a subject, responsible of a crime, is affected by a psychotic disorder (to determine he is unable to understand and want and he need to be cured) or if he has a normal mental state and so he must be punished by criminal law. This review is very useful to understand the state of art after 60 years of use of this technique, comparing healthy subjects with subjects at high risk for psychosis and from psychotic patient.