Expertise has played an essential role in the historical construction of juvenile violence as a social problem. The expert, who is situated at the centre and periphery of the child protection system, gathers the expression of violence and gives it form. In so doing, he/she contributes to a more complex definition of violence: from physical to psychic violence, and even to symbolic violence.
Since the 19th century, experts have moved beyond making simple diagnoses and entered the field of treatment of violence, joining others in the practice of care and rehabilitation. Physicians, psychiatrists, psychologists, pedagogues, sociologists and anthropologists have addressed the question of youth at risk, helping to define a target population for public policies.