People who write detective stories (or crime novels, or murder mysteries, or, in French, romans policier) are subject to strict rules. Their readers expect a specific type of honesty from them, and to break those rules is to risk getting your book thrown into the corner.
I personally have rules for when a book gets thrown, but since I read almost everything on the Kindle now, that has just become much harder. Nowadays I have to stick to the much less satisfying option of just deleting the book.
Authors of prizewinning literature will, of course, tell you that there are no rules for great literature. I concur – that has been proved over and over. But murder mysteries do have rules, and can tell you from first hand experience, since I’m working on one as we speak, that plotting them is rocket science! It is one of the most complex things I’ve ever done.
Anyway, the 20 rules were originally published in the American Magazine (September 1928) by by S.S. Van Dine, pseudonym of Willard Huntington Wright.
Twenty rules for writing detective stories (1928)
THE DETECTIVE story is a kind of intellectual game. It is more — it is a sporting event. And for the writing of detective stories there are very definite laws — unwritten, perhaps, but none the less binding; and every respectable and self-respecting concocter of literary mysteries lives up to them. Herewith, then, is a sort Credo, based partly on the practice of all the great writers of detective stories, and partly on the promptings of the honest author’s inner conscience. To wit:
1. The reader must have equal opportunity with the detective for solving the mystery. All clues must be plainly stated and described.
2. No willful tricks or deceptions may be placed on the reader other than those played legitimately by the criminal on the detective himself.
3. There must be no love interest. The business in hand is to bring a criminal to the bar of justice, not to bring a lovelorn couple to the hymeneal altar.
4. The detective himself, or one of the official investigators, should never turn out to be the culprit. This is bald trickery, on a par with offering some one a bright penny for a five-dollar gold piece. It’s false pretenses.
5. The culprit must be determined by logical deductions — not by accident or coincidence or unmotivated confession. To solve a criminal problem in this latter fashion is like sending the reader on a deliberate wild-goose chase, and then telling him, after he has failed, that you had the object of his search up your sleeve all the time. Such an author is no better than a practical joker.
6. The detective novel must have a detective in it; and a detective is not a detective unless he detects. His function is to gather clues that will eventually lead to the person who did the dirty work in the first chapter; and if the detective does not reach his conclusions through an analysis of those clues, he has no more solved his problem than the schoolboy who gets his answer out of the back of the arithmetic.
7. There simply must be a corpse