how to write detective story

If you want to write a detective story, you’ll have to begin with a little investigation of your own. There are several different sub genres in this category of mysteries; from hard boiled detectives to amateur sleuths.   You detective could be anyone, a little old lady, a cynical ex marine, a teen girl with a knack for mischief, a chef, even a couple of cats.
The first detectives of popular fiction were amateurs who solved murders like a parlor game outwitting the incompetent police.  Dashiell Hammett, a former Pinkerton detective, took a more realistic approach to crime solving, with classic detective novels like “The Maltese Falcon” and “The Thin Man.”  Raymond Chandler once said “He (Hammett) put these people down on paper as they were, and he made them talk and think in the language they customarily used for these purposes. He wrote scenes that seemed never to have been written before.”
Chandler’s Philip Marlowe epitomizes the hard boiled private investigator, a incorruptible, hard drinking, tough guy.  Chandler created a feeling of believability with his characters and stories.
Amateur sleuths are usually not held to the same standards. It can be tricky justifying the presence of your  protagonist especially if you intend to serialize the character.  Remember the Angela Lansbury from Murder She Wrote?  Every where she went a murder was committed.  I would serious reconsider a friendship with this type of sleuth.  Your detective has to have a legitimate reason to be involved and something personal at stake.  They may have been accused of a crime or the victim of a crime, they may be protecting someone else or they may have a professional interest in the truth, such as: journalists, lawyers or writers.
Once you’ve decided the type of detective story you wish to write, focus on the crime and facts of the case.   More than any other type of story, I believe the detective story will benefit from a detailed outline before you start writing.  There are certain rules you must follow to meet your readers’ expectations
1.  Introduce the crime early on, preferably within the first three chapters. It is the crime and subsequent clues that hook your reader.  The crime should be significant enough that your reader feels invested in the outcome.  Most detective stories involve a murder or kidnapping.
2. Introduce the detective and culprit early on.  You’re not playing fair if you don’t included the antagonist in the line up of suspects.
3.  Provide clues along the way so it is possible, though highly unlikely, that your reader could solve the case themselves.
4.  Don’t provide enough clues along the way so your reader solves the case before your detective.  A detective story is a race between your protagonist and your reader.  If the reader wins, the victory will be bitter sweet.  Your readers want to be challenged, but in the end, they want to be outsmarted.
5.  Wrap up all the loose ends.  Readers will remember every red herring you threw in their direction.  If a clue wasn’t relevant, make sure you provide a reason why it was included.    Each plot point must be plausible, and  the action even paced, without getting bogged down in back stories or subplots.
6.  Your detective must solve the case using logic or scientific means.  CK Chesterton wrote the following oath for all writers of detective stories: “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 on them and not placing reliance on nor making use of Divine Revelation, Feminine Intuition, Mumbo Jumbo, Jiggery-Pokery, Coincidence, or Act of God?”
Of course, the best way to learn how to write a detective story is to read detective stories.  Pay attention to how clues are revealed, when key characters are introduced and when revelations are made.  Detective stories are fun to read and fun to write, but if you don’t play by the rules, you won’t stay in the game.