Roger: Roger Simmons. What about the perfect crime?
Ironside: There are no perfect crimes, only imperfect detectives.
Roger: But it is possible.
Ironside: Perfect crime. Young people are always fascinated by the thought of it. Other people's errors look so obvious, so easy to correct. If X had not pawned the jewels, if Y had used another car; but X and Y are human. Being human they have flaws. Sooner or later they make their mistake. And having made their mistake, they are caught.