Analysis / Fair-Play Whodunnit

Van Dine's Commandments

Willard Huntington Wright under the pen name "S. S. Van Dine" has published "Twenty Rules for Writing Detective Stories", which can be treated as an extension of Knox's Decalogue:

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.
4. The detective himself, or one of the official investigators, should never turn out to be the culprit.
5. The culprit must be determined by logical deductions -— not by accident or coincidence or unmotivated confession.
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;
7. There simply must be a corpse in a detective novel, and the deader the corpse the better.
8. The problem of the crime must be solved by strictly naturalistic means.
9. There must be but one detective.
10. The culprit must turn out to be a person who has played a more or less prominent part in the story — that is, a person with whom the reader is familiar and in whom he takes an interest.
11. A servant must not be chosen by the author as the culprit. It is a too easy solution.
12. There must be but one culprit, no matter how many murders are committed. The culprit may, of course, have a minor helper or co-plotter; but the entire onus must rest on one pair of shoulders.
13. Secret societies, camorras, mafias, et al., have no place in a detective story. To be sure, the murderer in a detective novel should be given a sporting chance; but it is going too far to grant him a secret society to fall back on.
14. The method of murder, and the means of detecting it, must be rational and scientific.
15. The truth of the problem must at all times be apparent -— provided the reader is shrewd enough to see it.
16. A detective novel should contain no long descriptive passages, no literary dallying with side-issues, no subtly worked-out character analyses, no "atmospheric" preoccupations.
17. A professional criminal must never be shouldered with the guilt of a crime in a detective story.
18. A crime in a detective story must never turn out to be an accident or a suicide.
19. The motives for all crimes in detective stories should be personal.
20. A few of the devices which no self-respecting detective story writer will now avail himself of. They have been employed too often.