The Defective Detective is a trope that’s been around at least as long as the mystery genre in Western fiction, with Sherlock Holmes and C. Auguste Dupin of “The Purloined Letter” being sterling examples. (It’s possible it’s been around in Chinese and Japanese literature longer, given the rather odd behavior of some fictional judges, including one in Japan who had a tattoo (Gasp! Horror! Unbecoming of samurai!) and would use that fact to go undercover among criminals to roust out suspects.) Modern c-dramas include Su Ci of Maiden Holmes, who admits she’s not much good for anything besides solving cases, and pretends to be a man without much caring about it, and Commandery Prince An (Xiao Jinyu) of The Imperial Coroner, who… oh man, he goes well beyond nerd. If that character’s not officially a high-functioning autist he’s at least tap-dancing on the edge of the spectrum. A full list of his oddities would go on a while. So far in ep 9 he’s topped himself by casually revealing in front of the whole Imperial tea party that the device he just used to prepare exquisite tea is one he came up with to precipitate soil out of water samples when he’s trying to solve cases….
The Defective Detective is a classic trope, and used well, very effective indeed. It neatly solves two storytelling problems when you have a Great Detective as a main character. First, it lets you explain how on earth this detective always seems to know the one obscure fact that punctures a killer’s alibi, or allows him to track a suspect – or victim – to the ends of the earth. If the character’s hyper-focus and special interests all relate to crime-solving, then of course he’s got a whole library of said info in his head. Second….
Great Detectives are geniuses when it comes to investigation. That’s what we want; to see the truth laid bare in a single pulled thread, to see impossible murders solved, to see evildoers brought to justice – in a court of law if possible, dead in bloody self-defense if not. We want this. It’s part of the whole detective fantasy: that wrongs can be righted, the truth brought to light, and the trust of society shattered by crime at least partly made whole again. We need that genius.
But an actual genius is very, very hard to live with. If they’re so smart, why do they need anyone else? They run a risk of being someone the reader can’t connect to as a character, and that can wreck your whole story.
A Defective Detective, though? One who can track killers like a bloodhound, but can’t – quite – grasp the normal behavior of people at a party socializing? Who will, in fact, get in serious trouble if they try? They need someone who understands them. So Holmes has his Watson, Su Ci had Prince Qi, and Prince An has a tight group of friends and guards who do their best to make sure he’s got someone in his corner when the social stuff Goes Horribly Wrong.
A Defective Detective is someone broken in the eyes of the world, and thus even more driven to make what they can whole. They’re someone we can understand.
And if readers understand your characters, and respect them, they can grow to love them. And that will make your story stand out above all the rest.