Tips For Writing Sherlock Holmes-Style Detectives & Stories

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Know the difference between abduction, induction, and deduction.

These three concepts are very similar, so much so that many writers get them confused. Many characters described as using deductive reasoning are actually using inductive or abductive reasoning instead. There's nothing wrong with that, of course - all of these are potentially useful. It's just a good idea to get your terms right.

Deductive reasoning is essentially purely logical reasoning. For example:
"This animal exhibits all of the biological characteristics and behaviors of a dog. Therefore, it's a dog."

Inductive reasoning is based more in probability. For example:
"There's dog hair on the sofa, and a dog bed over in the corner. I can hear barking from the back yard. It's likely that whoever lives here has a dog."

Abductive reasoning is more about making a guess that potentially explains an observation. For example:
"There's a box of dog biscuits on the counter. Whoever lives here might own a dog."

Know how the logical processes work.

Poorly-written stories allow characters to get away with making logical errors left and right. For example, a box of dog biscuits left on the counter will be treated as conclusive proof of dog ownership in and of itself. Other possibilities, such as the biscuits having been left behind by a dog owner who moved out, or the biscuits being for the dog of someone who frequently visits, or having been bought as a gift for a dog-owning friend, will never be suggested, nor will the detective ever turn out to have initially made the wrong guess. Some authors do this kind of thing in an attempt to make their characters seem smart, in actuality the only way the detective would be right this often would be incredible luck.

It's important to remember that almost everything has more than one possible cause or explanation. A smart detective will consider all possible causes and look around to see what else is there that strengthens or weakens the likelihood of any given cause. For example, before deciding that someone who is coughing violently is seriously ill, the detective might look for other signs of respiratory illness - perhaps reddish, watery eyes or an inflamed nose, or a box of tissues nearby. Otherwise, it's just as possible that this person is coughing from having just eaten something that caused throat irritation.

It also can't always be assumed that one event is connected to another because they both happened around the same time. They might actually be completely unrelated, or they might both have been caused by a third factor. For example, a broken vase may have been knocked over during a fight that took place earlier, or it may have been knocked over by the cat later on. The repair guy who was over on the day of the robbery might be the culprit, or the real culprit might be a family member who was visiting that day. (And it's possible that the family member took advantage of the fact that a stranger was in the house to throw off suspicion!)

So bearing in mind that there are typically multiple, yet always finite explanations for any given scenario or situation, the detective will look around for anything that could indicate which of these possibilities are more or less likely to be true. Going back to the dog biscuit example, if there's a dog living in the house you'll very likely find things like hair on the floor and/or furniture, the smell of a dog, dog dishes, dog toys, and possibly even a dog bed. If none of these are present, it's unlikely that a dog lives here. It's more likely that the biscuits are intended for someone else's dog.

And of course, just because something is technically possible, doesn't mean it's worth considering, at least not at first. Some possibilities are just too unlikely to take seriously without having some compelling evidence for them. It might not be impossible that a complete stranger broke in and just left the dog biscuits just because, but since that's not a thing most people are very inclined to do, it's probably not what happened. "When you hear hoofbeats, think horses, not zebras" is something that any competent detective should remember and follow.

While the high-probability explanation isn't always going to be the right one, it's still the one that's most likely to be true and therefore is the least likely to be a waste of time to explore first. For the detective to seriously suspect something unusual, the common explanations need to prove inadequate - IE, there's stuff going on that the common explanations just can't account for, or the common explanations have all been proven wrong.

(If you haven't already, you should familiarize yourself with the scientific method and Occam's Razor. Both are very helpful here.)

Ultimately, when your detective finds an answer that turns out to be correct, you should be able to explain how your detective knows that this answer, and no other, is the right one. If you can't, what you've got is a character who jumped to conclusions and just happened to get lucky enough to jump on the right one.

Pay more attention to the real world.

The more you know about the real world and how it works, the more equipped you'll be to write a story about this type of character. So make a habit of paying attention to everything, particularly the hows and whys behind things. Again, there are typically multiple possible explanations behind anything, but these reasons are always finite. Figuring out the right explanation is a matter of systematically ruling out the others by working out which ones are impossible, or at the very least are just too unlikely to take seriously. But before you can do that, you need to know just what all these possibilities are. In addition, you also need to know that there's often a possibility of there being an explanation you don't know about yet, especially when you're a novice to this type of thing. Open-mindedness is vital!

And remember, there's no such thing as useless information here. Anything, no matter how trivial-seeming, can be very meaningful in the right context. Part of Sherlock Holmes's thing was being able to piece together something useful from even the most ordinary-seeming details, so if you want to write a character or story in this spirit you'll want to capture that aspect, too.

Make sure the clues are actually possible for the detective to acquire.

Make sure the detective finds and notices things in a way that actually makes sense. For example, when faced with something new and unfamiliar, people notice the big details first and the smaller ones later. It doesn't make a lot of sense for your detective to notice some microscopic detail on something within two seconds of seeing it for the first time.

You should also avoid having the detective notice things that would require superhuman senses to do so, unless these superhuman abilities are established to exist. (For someone like Sherlock Holmes, we can argue that he's very likely on the autistic spectrum, and one of his autistic characteristics is being more sensitive to stimuli than the average person. Of course, depending on the story/writer, he sometimes picks up on things that ought to be impossible, period.)

A few things to keep in mind:

• Light levels will affect what you see. Too dim or too bright, and you might not be able to see much.
• Ambient noise levels will affect what you hear. Too much ambient noise and you'll be less likely to pick out an individual sound among them, especially if it's soft. In a very quiet room, you can hear a pin drop.
• Temperature and humidity will affect what you smell. For example, it's harder to smell anything if temperatures are below freezing. Biological objects don't decay, smellable particles can't escape into the air from frozen objects, and the lack of humidity makes it even harder for what particles there are to reach your nose.
• Distance affects everything. The further you are away from something, the less likely you are to be able to see, hear, or smell it very well.

(You can experiment with this yourself. Pay attention to what you can pick up on in different environmental conditions. For example, what you can smell on a hot, dry afternoon will be very different from what you can smell on a cool, damp evening. What you hear during the daytime, when traffic and birds are more active, will be different from what you hear at night.)

Likewise, if your detective hecks off alone for awhile and later comes back with some salacious clue in hand, how did the detective actually get it? Can you describe the process step-by-step? If so, is that how things actually work, or at least how they work in this universe? If you can't answer all of these questions satisfactorily, you have a plothole on your hands - and that's not good for a story that puts so much emphasis on using one's brain.

Make sure the clues actually mean what you say they mean.

It's also important to make sure that the clues (or lack thereof) you present in your story genuinely point to the conclusion your detective is actually supposed to draw from them. BBC Sherlock is actually pretty bad at this. For example, in A Study In Pink, Sherlock determines that a woman has been cheating on her unhappy marriage for some time now as the outside of her wedding ring is damaged (supposedly indicating that she hasn't been getting it polished) while the inside is smooth (supposedly indicating that it's received polish by being taken off and put back on so often). But there are two big problems here: first of all, the outside of a gold band like that would still be abraded simply from rubbing up against her index and pinkie fingers while worn, as well as from her fingers rubbing against the outside while removing it. In addition, there's no good reason for the inside of a wedding ring to be damaged at all - what could possibly be rubbing against the inside to scratch it up? So in reality, the woman's wedding ring just doesn't say what the story claims it says.

A similar problem occurs in The Great Game, where Sherlock determines that a cut on a dead woman's hand was inflicted post-mortem because of a lack of blood around the wound. In fact, the lack of blood says absolutely nothing, as it's possible (even very likely) that the coroner has already washed the corpse off. What actually gave away the wound's post-mortem status was the lack of bruising and inflammation around it, but the story treated this as irrelevant - it was supposedly the lack of blood that gave it away.

So put some thought and even research into making sure that your clues actually say what you need them to say. While you're writing them, look at what you've got and ask yourself if it's possible - or even more likely - that they point to something else. If that's the case, you need to change something. You don't want to end up with something as cringeworthy as your character deciding that someone is an alcoholic when Parkinson's, multiple sclerosis, or even nerve injury are all possibilities.

About making other characters feel unintelligent or uncomfortable...

Making other characters feel unintelligent or uncomfortable might be hard to avoid sometimes, but people who go around casually revealing everyone's personal secrets or intentionally show off their skills to make everyone else feel inferior are mean.

Revealing people's personal secrets is a violation of privacy. It's not a whole lot different from rifling through someone's trash to find a shopping receipt with a few embarrassing items on it and reading them out loud to everyone, or reading someone's private diary aloud. (Can you imagine how you'd feel if someone did that to you or one of your friends?)

Now, this is not to suggest that saying things that make people feel uncomfortable is always wrong or inappropriate. Sometimes uncomfortable things simply have to be said or done in the interest of solving a case. The question is, is your detective genuinely saying or doing this because there's no other choice, or is it just for the sake of ruffling someone's feathers? And if it is for a case, is it actually the only option, or is the detective just using the fact that it's for a case as an excuse?

"What if my detective just has bad social skills?" some of you might ask. Here's the thing: people with bad social skills are still fully capable of learning better ones. Just because they have a bad grasp on norms and boundaries doesn't mean they can't understand and appreciate them once they've been explained, and it doesn't mean they can't understand and appreciate that what they've done is genuinely hurtful or distressing. They can also try to apologize to those they've hurt and make an effort to do better in the future. This is what sets a well-meaning person with bad social skills apart from someone who is just plain mean, uncaring, or selfish. So if you want to write a detective who is merely awkward and not a bully, keep this in mind.

And of course, this isn't to say you can't write a mean detective (or a detective with a mean streak), either. However, you should always maintain awareness that this character's behaviors are mean. There's nothing cool about this behavior, and there's nothing amusing about being treated this way. You might also find How To Write Sympathetic Antagonists Without Endorsing Or Excusing Their Actions, & Without Making Your Protagonists Seem Heartless and Tips For Writing Lovable Jerks useful.

And a few more things!

Everything should work the same way it does in the real world except where otherwise made clear to the audience. If fantasy or science fiction elements are involved, the audience should be made aware of them and understand that they are a valid possibility before the mystery is solved. Deliberately keeping the audience ignorant to keep them from guessing correctly can make them feel cheated once they learn that they had no hope of ever figuring things out for themselves.

It's okay for your detective to have to pick someone's someone else's brains, or for someone else to notice or figure something out. Nobody knows everything and nobody can notice everything, so having this happen can add add a bit of realism. Plus, it helps you avoid the problem of having a character who is only smarter than everyone else simply because everyone else is cartoonishly daft.

Make the Watson useful, if you've got one. The Watson doesn't necessarily need to be a crack detective, but should fill some role beyond serving as a sounding board for your detective. Maybe the Watson has some knowledge or skill that the detective doesn't, or can explain or clarify things that the detective doesn't quite understand. Whatever you do, try and make sure this character actually does something that moves the plot forward. And please don't make the same mistake as BBC Sherlock and act like this character serves as a moral/emotional compass for the detective when the detective never actually listens to a word this character says.