The Ten Rules of (Golden Age) Detective Fiction

In the 1920s mystery author, critic and clergyman Ronald Knox developed Ten Commandments he believed a crime fiction author of the ‘golden age’ ought to adhere to. By abiding by these rules, an author could ensure their work was worthy, unlike what he coined ‘shockers’; mainstream mysteries that he felt tricked the reader.

The Detection Club

Knox’s list was adopted by the Detection Club, who came to consider his rules as a code to write by. The Detection Club was a sort of guild created in 1930 by leading British detective fiction writers including Agatha Christie, Dorothy L. Sayers and G. K. Chesterton. The club allowed writers to meet over dinner and discuss their work or solve technical issues.

Admittance to the club required taking ‘the oath’ which went as follows:

“Do you promise that your detectives shall well and truly detect the crimes presented to them using those wits which it may please you to bestow upon them and not placing reliance on nor making use of Divine Revelation, Feminine Intuition, Mumbo Jumbo, Jiggery-Pokery, Coincidence, or Act of God?”

The club became known especially for the publication of ‘round-robin novels’, whereby an author would complete a chapter without knowing how the next would be completed. The most famous of these is The Floating Admiral.

The Detection Club still meets three times a year for dinner and is currently presided over by Martin Edwards. Admission is by invitation-only, so you know you’ve hit big time if you’re asked to join!


The 10 Rules – Do They Still Stand Up?

Let’s take a look through the ‘rules’ and see which are still true of modern crime fiction – remember that these were written back in the 1930s!

#1 The criminal must be someone mentioned in the early part of the story, but must not be anyone whose thoughts the reader has been allowed to follow.

I totally agree with the first half of this statement, we should have the killer introduced within the first act of the story if said story is a ‘whodunnit’. Though I think it is entirely reasonable to have included scenes from the killer’s point of view.


#2 All supernatural or preternatural agencies are ruled out as a matter of course.

Now, this is one we have seen broken often in modern crime fiction. Take Peter James’s Roy Grace for example, who visits a psychic for help with his investigations.

I do think though, that we should always rule out solving a crime by magic unless the pretence of a magic world is described to the reader. I would also be pretty annoyed if a ghostly apparition came to the main character and told them where the killer is lurking.


#3 Not more than one secret room or passage is allowable.

I’m not sure how well a secret passage works in modern crime fiction unless the setting has some sort of background that would imply a secret room or passage is feasible. For example, if the setting is an ancient house or has ties to the Illuminati or something. Or maybe a modern example would work if the house owner is paranoid or believes in preparing for the end of the world with an underground bunker.


#4 No hitherto undiscovered poisons may be used, nor any appliance which will need a long scientific explanation at the end.

I think most crime readers would feel cheated if the answer to a crime was something they didn’t understand or hadn’t come across. It feels like cheating. I guess though if you had eluded to, let’s say, a suspect who has a keen interest in torture chambers or building contraptions, an unusual method of killing would, therefore, be assumed.


#5 No Chinaman must figure in the story.

On the surface, this sounds racist but a little digging tells me that this rule was meant to prevent the overuse of the clichéd Chinese character in British mysteries. A modern version might be ‘no alcoholic detectives’!


#6 No accident must ever help the detective, nor must he ever have an unaccountable intuition which proves to be right.

At first, I thought this was a little unfair and was thinking back to all the times Poirot has an intuition about what has occurred, where the missing weapon is, how that poison was administered. But the point here is that Poirot can always explain his method in a way that makes sense; the reader could also have had this intuition themselves. For example, Poirot wouldn’t have ‘an intuition’ that the weapon was hidden in a teapot because he split his this morning and thought it was ‘a sign’!


#7 The detective must not himself commit the crime.

Fair enough I think unless the detective has been set up throughout the story as a shady character. If you can write this outcome without it being a surprise to the reader then I think you’ve done well!


#8 The detective must not light on any clues which are not instantly produced for the inspection of the reader.

I think this one still holds up. It’s not fair to keep a vital piece of the puzzle from a reader, only to present it, later on, to move the story forwards. I guess this could be broken if there is a good reason for keeping a clue from the reader, e.g. a dirty cop has deliberately kept evidence from the team and we all find out at the same time.


#9 The stupid friend of the detective, the Watson, must not conceal any thoughts which pass through his mind; his intelligence must be slightly, but very slightly, below that of the average reader.

Now, this is a little harsh, Watson was a trained doctor after all! Also, crime fiction is massively popular these days, how would you decide the IQ of an ‘average’ reader?!

I’m not sure there is a place for a ‘stupid’ sidekick in modern fiction because a reader simply won’t believe that a homicide team could be made up of unintelligent detectives. This may work if your main character is a private investigator, however, and could make for some interesting dialogue!


#10 Twin brothers, and doubles generally, must not appear unless we have been duly prepared for them.

I had to laugh at the thought of a writer magically pulling an unknown twin from thin air, without having hinted at it beforehand. I don’t think this would fly with any modern reader and would swiftly generate lots of negative reviews!


Over to you

Which of these do you think crime fiction should follow, or discard? Which would you add? Let me know your thoughts in the comments!

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