How measurements helped to catch criminals in the 19th century

You will never find a person who has absolutely same physical parameters with you. Even if you have the same height with your friend for example, your fingers will be different. There are no 100% same people in the world. And this peculiarity helped to catch criminals in the 19th century.

In 80s of the 19th century it was difficult to identify repeat offenders. For this purpose police used special card indexes which included questionnaires with verbal descriptions and photographs of detainees. But such cards were far from perfect since the verbal descriptions looked too general and average to let the police confidently identify someone. There were thousands of criminals of “average” appearance. At that time a repeat offender who had been caught could only use a different name and the whole system immediately broke down – his last name was not found in the card index. Such person was considered accidentally stumbled, not an experienced criminal.

Alphonse Bertillon who worked in Paris police and fulfilled such cards understood that his long hours work was absolutely useless. He thought such system could be revised and improved. Being a son of anthropologist he believed that people could be identified through physical characteristics and therefore he decided to try anthropology method to improve descriptions of suspected criminals.

Bertillon took measurements of certain bony portions of the body and confirmed that people could have only several anthropometric indicators that could coincide. Four, five or more at the same time never did. He calculated that if you take 14 different indicators (height, length of the upper body, circumference and length of the head, length of the feet, arms, fingers and ears, etc.) of an adult, then the chance of a match according to probability theory is 1: 286 435 456.

Special new card indexes were created basing on anthropometry and after several successful and high-profile cases of identifying criminals Alphonse Bertillon was called a genius and the system he invented was named after him.