Bertillon, a French criminologist, believes that "every measurement slowly reveals the workings of the criminal." The creator of what is known as the "Bertillon System," measures the length and breadth of the head and the length of the middle finger, left foot, and forearm to identify the physiological characteristics of a criminal. Using measurements and photography (now known as the "mugshot"), he keeps extensive records through a filing card system of incarcerated and/or arrested people.

This is the first "scientific" tracking system to be used by police. It will first be used in the U.S. in the 19th century to track Black women sex workers in Minneapolis, Minnesota. However, the women will attempt to thwart the system by all using the same alias name, "Mamie," so they can't be surveilled.