WMG / The Brothers Karamazov

Dmitri did kill his father, not Smerdyakov.

Smerdyakov would have to enact quite the Gambit Roulette to pull off the frame-up that the novel posits he does. Given the sheer amount of evidence, and the fact that the murder is committed off-page, it honestly is more believable that Dmitri really is the killer. The only confirmation in the book of Smerdyakov doing it happens from Ivan's perspective, who's going through a brain fever-induced mental breakdown and is known to suffer from hallucinations. It's quite possible that Ivan imagined Smerdyakov's confession and personally provided the money he used as evidence at the trial.