by Robin Spano
Answer to Part 1 (Do you know who did it?) – When I start a novel, no, I don't know who the killer is. I generally open with a premise, populate a few chapters with a supporting cast of suspects, and once I'm pretty sure I've met all the players, I look at them to see who I think is a good candidate for the killer. I keep it open for myself through the entire first draft, though. I like to suspect them all, so that each character is naturally given a reason for a reader to suspect them, too.
Answer to Part 2 (How do you keep it from the reader?) – It's impossible to know how well you've hidden your clues. Like Susan said yesterday, it always feels like the clue is big and bold and way too obvious, even when hidden in the middle of a sentence in the middle of the book. But you need ample clues, or you're not playing fair with the reader. (Who wants to read a mystery where the killer is the postman you met on page three and never saw again until the detective visits his house at the end to accuse him?) So before publication, I ask as many of my loving family members who are willing, and friends if they express interest, to read the draft and tell me:
(a) When did you know who the killer was?
(b) Were there enough clues that you felt like you could have guessed if you tried?
I collate their responses as I revise the MS into a closer-to-finished draft. I think the ideal mystery novel has about ten percent of readers seeing the right answer from the outset, and ninety percent left hanging until the end. This way you know that the clues were fair and in the right places, but the story obfuscated them for all but the most eagle-eyed readers.