"In fact, little is known about any of the people whose photographs appear in this book - who they were, where they came from or where they went. We know even less about the police who took the photographs or, indeed, why they took them. What we do know is that sometime around 1910 Sydney police began making informal mug shots of some of the people who passed through Central and other inner-city police stations. Only a small number of the tens of thousands of housebreakers, thugs, gunmen, shoplifters, thieves, prostitutes, drug addicts, perverts, pickpockets, brawlers, derelicts, hooligans, confidence men, confidence women and confidence children arrested were ever photographed. But by 1930 there were more than 2000 of these portraits.
We don't know why these particular people were chosen. A single paragraph in a police booklet from 1935 mentions the work of the 'expert photographers' of the Photographic Section, who took portraits of people 'when in the opinion of the arresting Officer the offender is liable to lapse into a life of vice and crime'. The gallery of 'Special Photographs', as they were called, seems to have been intended to help police distinguish the professional, in-for-the-long-haul players from the hordes of simply unlucky, momentarily foolish or temporarily erring citizens. Police were expected to be able to recognize professional criminals by sight, and various methods were used to help that recognitions."