 What happens to the Ex members who think about committing a crime?
A civilization weary of murder, robbery, kidnapping, counterfeiting, blackmail, rape, arson, and drunkenness had originated the CPA—Crime Prevention Association. There were no longer any prisons—CPA officials had declared loudly and emphatically that their job was to prevent crime, not punish it. Instead, he was sent to a hospital where all criminal tendencies were removed from his mind by psychologists, shock treatments, encephalographic devices, a form of prefrontal lobotomy and a dozen other methods. And therefore, an EX (a convicted criminal who received the treatment was commonly called an Ex because he was in the strictest sense of the word an Ex-criminal) ... On the other hand, attempted murder, robbery, kidnapping, etc., were not crimes.
 They feel immense head pain at the thought of crime.
 They are unable to think about crime.  They are locked back away in the hospital for more treatment.  They are given another DCT card.  They feel immense head pain at the thought of crime.