In the Nineteenth century in Europe it is launched the debate on “Crimes without explanation”, those crimes apparently deprived not only of any logical, but also of the will of their author. Justice comes into crisis. At the same time, the nascent psychiatry proposes an explanatory model that replaces the freedom of action with the presence of a psychiatric illness at the base of what has been done. The person is considered, due to this disease, not aware to respond to the consummation of his actions. He is a person incapable of understanding and willing, a dangerous one – they will say – from whom the society must be previously protected, through a security measure. So that of the dangerousness is a precautionary discourse, founded on the culture of risk prediction and finalized to put in action a horizontal control act over individuals. A contradictory, unconstitutional and unjust mechanism, which remains in force despite, with the Law 81/2014, a first step towards its dissolution has been taken.

Keywords: Dangerousness; Security Measure; Penal Code; Psychiatry.