Exactly. The good old mystery novels from the golden age followed some rules, more or less, to prevent that.

Ihihi... it took me a good while to understand those rules, but a dear friend of mine made sure I got them right.

The culprit must be mentioned in the early part of the story. Nothing supernatural can be used as detective technique. There must not be any hidden passages or doors. No mysterious drugs or weird 'scientific' devices that no one understands. The detective can't rely on accidents or intuition. The detective can't be the culprit. The crime can't be solved with clues not presented...

Heh heh, I still remember most of it, I'm surprised!