The purpose of this paper is to explore the role of mental health experts in Italian Judicial System through a historical approach. First of all, it will be analysed the current use of brain science in assessing criminal responsibility, by retracing the so-called neuroscientific paradigm, which considers thoughts as a result of synaptic connections, mere brain images to be captured by fMRI, and that is now permeating all areas of knowledge. It is therefore not surprising that these techniques, far from remaining closed in aseptic laboratories, have now entered even the austere courtrooms. So, faced with the disintegration of the power of psychiatrists and their expertise, now deemed less objective and less certain, in the courts the judges are increasingly choosing to rely on techniques that appear more "certain" and "infallible" than others. If once new technologies were mostly used during the investigating period preceding the trial, now the possibility of “reading the brain” of the accused, seems to be a new and unsettling reality of modern trials. Secondly, it will be examined whether the entrance of neuroscientists in courtrooms represents a novelty, in order to understand continuities and discontinuities between old and new kind of expertise. Indeed, judges every day have to decide on the mental capacity of the accused, for the purpose of to distinguish who must be punished from who must be cured. In spite of the Latin maxim ‘iudex peritus peritorum’, they have been appointed experts witnesses to make this problematic decision, since the nineteenth century, when the “alienists” like Cesare Lombroso had entered in courtrooms. After that, new experts such as psychiatrists, criminologists, psychotherapists, psychoanalysts (and today neuroscientists and geneticists) cooperated with judges holding an unchanged role: that of ‘truth-seekers’ or last delegates of the oracle.