Originally my third chapter was going to be about an unknown killer who may or may not had accomplices and that everything will be revealed at the terminus of the book but I decided that my third chapter will be an interview of a serial killer who is a cross between Dean Corrll, John Wayne Gacy, and Herbert Baumeister. I was hoping to write it in a way that creates doubt about if he had accomplishes and whether or not he really did anything. And towards the end of the book the killer along with his alleged accomplishes will mysteriously commit suicide much like what happened in a famous case in Pakistan, i.e., Javed Iqbal!
There is an episode of Deep Space 9 called Duet where they did exactly what you're trying to accomplish. Now the nice thing about Deep Space 9 is that you don't need to know anything about star trek to enjoy that series. It is an episode where a man is captured and accused of war crimes. What made this episode so good is that you did waiver between skepticism and certainty. Eventually, you just stop trying to speculate become engulfed in how it's going to end. I suggest checking it out.