"I'm not smart," I said. "I've always assumed that the so-called 'perfect crime' would be one in which the criminal walks off scot-free with the loot under one arm and the girl on the other."
He said, "From your point of view, a true 'perfect crime' would be one in which no clue existed, including the fact of the crime itself—except those clues that were deliberately planned by the perpetrator for some purpose of his own. That is your own angle, isn't it?"
I nodded. Indeed it was, and it had been expressed in precisely the same words that I had used in speaking to Chief Weston.
"However," he went on blandly, "you'll agree that a clue is usually the result of a mistake, or failure to plan completely, or the result of some accidental circumstance."
"Right."
"But in a 'perfect crime' there would be no error, no mistake."
"Yes, but aren't you backing yourself into a hole that you've lined with fish hooks yourself?"
"Not at all," he replied. "Clues must be cleverly contrived, created, and established in such a way that the episode is ultimately known to be crime and not labeled misadventure, suicide, or the like. Otherwise," he said with a genial smile, "we're writing about a 'perfectly justifiable homicide' instead of a 'perfect crime.'"
I nodded again.
"And, of course," he finished, "these clues must also provide precisely the correct amount of information so that the motive of the criminal is not only fulfilled, but exposed—if not to one of the characters in the book, at least to the reader."