The annals of crime are thick with thieves.
Until the late 19th century—and in many places, well into the 20th —the identities of arrested criminals were kept in bound, specially ruled notebooks, like accountants’ ledgers. Criminals were booked in chronological order, by their stated name, and sometimes with a few words of description. Vague details, poorly expressed: age, occupation, eye color, scars.
You would find a thousand stories flipping through the crumbling pages of such a book.
What you would not find is any particular person you might be looking for. You would not have at your fingertips any way of comparing a criminal whose collar is under your thumb to criminals who had been caught before in your city, let alone criminals roaming the surrounding counties and countries, those who had crossed borders to evade the law, to evade any recognition of their faces or names or their M.O.s.
Enter Alphonse Bertillon, of the Paris police department. One of his century’s most brilliant bureaucrats, he would not be outfoxed by these slippery and changeable identities.