This chapter will explore in depth two works on criminality and regimes of discipline. I, Pierre Rivière, Having Killed My Mother, My Sister and My Brother: A Case of Parricide in the Nineteenth Century (1973) is a collection of legal and medical reports, accompanied by a long and extraordinarily detailed written confession by a French peasant who, in 1835, murdered his mother and siblings. The documents are edited and commented on by Foucault and his team of sociological researchers. Foucault's interest in the case lay in its susceptibility to be read according to the method of genealogical research he adapts and borrows from his readings of Nietzsche (see pp. 12–16 of the present book), which proceeds from the postulate that knowledge is produced as the effect of local operations of power. The case of Rivière afforded the opportunity to reflect upon the ways in which the murderer became the ground for a discursive battle between and among the contemporary medico-legal disciplines. It is a good example of Foucault's notion that force fields of discourse constitute individuals according to discrete categories of social subject, in this case criminal/medical categories.