Hooton believed in Cesar Lombroso's theory of the born criminal, which held that criminals could be identified by their physical characteristics. His measurements included such physical characteristics as weight, height, head length, nose height, and ear length. Hooton felt that it was necessary to differentiate among the various criminal types in order to provide a clearer picture of deviant behavior. He saw the deviance caused by the groups as particularly troublesome because the heterogeneity of backgrounds had to be accounted for in the measurement of their deviance. Criminals are excessive in extractive, laborer, and personal service occupations, and deficient in trade, professional, and clerical occupations.
Criminals are greatly inferior to civilians of the same ethnic origin in educational attainments.
Tattooing is commoner among criminals. Criminals have thinner beard and body hair, more straight and less curved hair, more red-brown and less gray and white hair. Dark eyes and blue eyes are deficient in criminals, while blue-gray and mixed eyes are in excess. Low sloping foreheads, high nasal bridges, and thin lips with compresses jaws are prevalent in criminals. The criminal ear is more likely to have a slightly rolled helix and perceptible Darwin's point than the civilian ear.