Lombroso, an Italian physician, wrote a book called, 'L'humo Delinquente' within which he suggested criminals are 'genetic throwbacks' a primitive sub-species who were biologically different from non-criminals.
By today's standard, his methods would be described as speculative but he is credited as moving criminology into a more scientific realm and he laid the foundation of modern offender profiling.
Lombroso states offenders as lacking of evolutionary development and their savaged nature meant that they found it impossible to adjust to demands of society and inevitable turn to crime.
Criminal sub-type identified as being possession of particular physio markers that were linked to particular types of crime. These are bio determined atavistic characteristics, mainly features of the face/head that make criminals physically different from us.
Murderers described as having blood shot eyes, curly hair, long ears. Sexual deviants described as having glinting eyes, fleshy lips and projecting ears. Also, criminals are insensitive to pain, use criminals slang and having tattoos.
Examined facial and cranial features of hundreds of Italian convicts and proposed association. Skulls of 383 dead criminals and 3839 living Concluded 40% of criminal acts could be accounted for by atavistic characteristics