 Why was the girl unable to help Joe commit his planned crime?
A civilization weary of murder, robbery, kidnapping, counterfeiting, blackmail, rape, arson, and drunkenness had originated the CPA—Crime Prevention Association. 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. A crime because it theoretically inflicted psychological injury upon the intended victim—and because millions of women voters had voted it a crime. On the other hand, attempted murder, robbery, kidnapping, etc., were not crimes. Joe discovered to his dismay that the girl was telling the truth when she said she was a sergeant in the WSDA.
 She was a part of the WSDA and obviously knew how to defend herself.
 She was a part of the CPA and didn't agree with his idea.  She was unable to accept his small payment for a large possible consequence.  She was a part of the WSDA and obviously knew how to defend herself.  She knew no one would believe that he had actually tried to rape her because of her status as a DCT.