In Roald Dahl's novel Matilda, Miss Agatha Trunchbull has undoubtedly committed enough crimes to spend a long time in prison if she's ever caught.
She used cruel punishments on the students in her school. She kept Miss Honey in slavery throughout most of her childhood, forcing her to do all the housework. When Miss Honey has grown up, Miss Trunchbull stole her wages, and borrowed her inheritence.
But the book suggests one more possible crime to top this.
[…] Miss Honey said, hesitating, “You see, no one could believe that he [Miss Trunchbull's brother-in-law, Magnus] would ever have done it. He was such a very sane and sensible man.”
“Done what?” Matilda asked.
Matilda was stunned. “Did he?” she gasped.
“That's what it looked like,” Miss Honey said. “But who knows?” She shrugged and turned away and stared out of the tiny window.
“I know what you're thinking,” Matilda said. “You're thinking that the aunt killed him and made it look as though he'd done it himself.”
“I am not thinking anything,” Miss Honey said. “One must never think things like that without proof.”
Do we ever find out, from the novel or from other sources, whether Miss Trunchbull has indeed killed her brother-in-law?