The invention of photography ... is no less significant for criminology than the inventing of the printing press is for literature. Photography made it possible for the first time to preserve permanent and unmistakable traces of a human being. The detective story came into being when this most decisive of all conquests of a person's incognito had been accomplished. Since then the end of efforts to capture a man in his speech and actions has not been in sight. Walter Benjamin, Baudelaire