One of the most common things I see in early drafts of writing is authors feeling the need to spell it out for readers. Stuff like “It didn’t make sense” or “That meant Martha had to be the killer” are sentences that make your reader feel like you’re coddling them. If you explained the situation well, then the reader should be able to understand what you’re trying to get at.
This is why villains tend to go on huge monologues; the writer fears that the reader won’t understand everything if she doesn’t. While there are some things that you might need to say just to establish something, most feelings and revelations shouldn’t rely on this. Show, don’t tell, right? Foreshadowing, good characterization, and description go a long way in leading readers to your intended idea, and they’re not lazy cop outs.
Aim for your audience to understand things in time with the character. Let them realize it with the character and enjoy the fact that they came to the right conclusion on their own. Of course, this is a double-edged sword. If you’re too vague, readers might be confused. Being able to do this – and do it well – is not easy, and it’s going to take a lot of work to get good at it, but it’s worth it. Practice it. Implement it. Your work and your readers will thank you for it.