Dr. Grimesby Roylott trains his snake to climb down a false bell pull to bit Julia Stoner in her sleep. So, while the snake's poison kills Julia Stoner, it is widely held that Dr. Roylott is her murderer.
At the end of the story, Holmes remarks that he feels no guilt for HIS responsibility in turning the snake on Dr. Roylott. This epitomizes the notion in detective fiction that poetic justice is justice. (Roylott dies at the wrong end of his own tactics)