agathaThe seeds of the detective fiction genre were planted with Poe’s 1841 publication of The Murders in the Rue Morgue, but it was The Moonstone by Wilkie Collins (1868) that introduced many of the now classic features of the genre – viz – a country house robbery, a celebrated investigator, bungling local constabulary, false suspects, the ‘locked room’ problem, the ‘least likely’ suspect solution.  By the 1920/ 1930s the genre was firmly established, and enjoying a golden age, seeing stories published by the ‘Queens of Crime’ – Agatha Christie, Dorothy L. Sayers, Ngaio Marsh and Margery Allingham, who introduced us to detectives such as Hercule Poirot, Miss Marple, Lord Peter Wimsey, Chief Inspector Alleyn, Albert Campion (and less well known – Sayers’ other amateur detective – the wine salesman Montague Egg). The golden age helped cement the various characteristics (clichés even) that modern audiences feel are indicative of the genre.
In 1929 the crime writing priest* Ronald Knox wrote his Ten Commandments for detective fiction:

1. The criminal must be mentioned in the early part of the story, but must not be anyone whose thoughts the reader has been allowed to follow.  
2. All supernatural or preternatural agencies are ruled out as a matter of course.  
3. Not more than one secret room or passage is allowable.  
4. No hitherto undiscovered poisons may be used, nor any appliance which will need a long scientific explanation at the end.  
5. No Chinaman must figure in the story.
6. No accident must ever help the detective, nor must he ever have an unaccountable intuition, which proves to be right.  
7. The detective himself must not commit the crime.  
8. The detective is bound to declare any clues upon which he may happen to light.  
9. The stupid friend of the detective, the Watson, must not conceal from the reader any thoughts which pass through his mind; his intelligence must be slightly, but very slightly, below that of the average reader.
10. Twin brothers, and doubles generally, must not appear unless we have been duly prepared for them.

Here’s my somewhat haphazard thoughts on these points:

The general intention appears to be to establish a code of fair play – a notion that feeds into the idea that a massive part of the appeal of detective fiction is its ludic quality. Readers are entitled to feel cheated if authors do not play by the rules of the game. Rules are there to be broken though, and most detective fiction authors technically break most of Knox’ rules at some point. However, they usually adhere to the general ethos of fairness – I’ve rarely come across a detective story solved using a deus ex machina, for instance – such a device effectively undermines whatever plot has preceded it, and I can’t really see any author or reader of this genre being satisfied with such a solution. Point 10 raises a crucial point – we must be ‘duly prepared’ for anything which would otherwise act as a deus ex machina. It is not fair to suddenly introduce elements that are unlikely – such as the supernatural, twins, obscure poisons or a secret passage. It is like getting to the World Cup final and finding out that a country that hadn’t even qualified at group stage is being allowed to play. It’s just not cricket.

I’m not perfectly convinced by point 8 – I suspect what Knox meant is that the author (not the detective) must at least hint at all clues, so the reader can play the game and fashion them into a theory, should they spot them. The detective doesn’t need to explicitly relate the significance of clues at the same time as the reader, indeed this could have the effect of revealing the solution too soon. Knox’ insistence on transparency of the detective’s thought process and method is not helpful – yes it might make the game fair, but it makes for a rather poor storytelling experience. Good writers, I think, manage to balance game play and storytelling, so we feel we have had a good shot at solving the mystery ourselves, but also that we have allowed ourselves to be taken on a journey where we trust in the detective, even when they don’t show their working. Otherwise we may as well just play Cluedo.

Point 9 highlights a useful device of the genre – this enables the reader to position themselves between the ‘stupid friend’ and the detective – the detective is a few steps ahead of the reader, and the ‘stupid friend’ helps check the pace of the detective so the reader is not rushed, but simultaneously allow the reader to feel clever because they understand more than the stupid friend does. They also help the author to develop red herrings, and they question the competence of the detective. Hastings, Poirot’s flatfooted sidekick seems to spend a lot of time bemoaning Poirot’s lack of action whilst Poirot mulls things over. Hastings is pretty much always wrong, come the end, and the reader, who has always trusted in the detective’s approach, is vindicated.

Misdirections in detective fiction are often achieved by toying with these rules. There is at least one Agatha Christie story that stretches point 7 – the denouement reveals the killer to be the local policeman who has been closely involved in the investigation.  Written effectively, you are lulled into a false sense of security by attributing the immunity of the main detective (who usually is beyond suspicion) to any associate detectives, professional or otherwise – a misjudgement, as really, everyone, apart from the main detective is fair game, regardless of status.

Knox’ points provide an ok starting point for thinking about detective fiction but aren’t exactly a definitive set of rules for the genre, unsurprising really, given that the bulk of the writing in the genre came after their publication! In a later post I shall tackle Van Dine’s Commandments.
(The initial impression given by Point 5 is one of outdated racism, but there must be more specific reasons why Knox felt it necessary to make a point of it. I’d be interested in hearing what explanations people have for the exclusion of Chinamen from detective fiction).
*crime fighting priest = Father Dowling.