Now, I know we all have different ways of writing and any ‘rules’ that exist are made to be broken, but when you are starting to plan a crime fiction novel, there are a few things that are generally accepted as universal truth (except, of course, where they aren’t).
The crime needs to be big enough to sustain the book
This one almost goes without saying. You need to be writing about a crime significant enough to merit a whole novel. Often in crime novels, this will be murder, but it doesn’t necessarily have to be – it just has to be big enough to be interesting and sustain our interest right to the end.
The murderer needs to be capable of the crime
Assuming your book is about murder(s), the culprit needs to have the capacity for the crimes committed. This means they need to have the motive, the means and the physical capability (double bluffs where they appear to be entirely innocent/incapable before the big reveal are allowed). The criminal should also generally appear in the book – not necessarily extensively and not necessarily that early on, but their presence should be enough that we don’t feel cheated when the reveal comes.
The crime needs to be possible
The crime committed in your story might seem impossible – impossible to commit, impossible to solve. That’s part of the fun of detective fiction. But ultimately, it needs to be possible. We need to know how it was carried out and how it was solved, otherwise the reader is just going to be left feeling frustrated.
The crime should be solved by detection
Of course, coincidences exist in real life. They can exist in crime fiction too, but if your solution comes about because of one big coincidence, it’s not going to be particularly satisfying. The murderer/outcome should ideally be revealed through detection and logic. Which brings us to the next point…
Your detective needs to be capable of detection
The detective is how the reader learns about the story behind the crime, and it is something of an unwritten rule in crime fiction that your detective actually needs to be good at their job. An incompetent detective might be good for a minor character, but we want the main character to be the one who works it all out at the end.
The crime needs to occur early in the novel
Many crime novels have the crime occur before the start of the book, others within the first few chapters. Others have the crime that gets the ball rolling near the start and then have further crimes throughout the book. However you decide to do it, the plot needs to get going pretty quickly.
You need a reason to keep on reading
A large part of the appeal of crime novels lies within the tension, so we definitely need a good reason to keep reading until the end. You might reveal your murderer halfway through the book, but there are still ways of making it compelling right until the last page. Twists, turns and surprises are almost never unwelcome in crime fiction.