A Swiss immigrant to England, Manning is on our list not so much for the scope of her crimes (she had only one victim) as for the sensation her crime spawned.
Marie had two suitors - a young man close to her age named Frederick Manning and an older gentleman named Patrick O'Connor - who both proposed marriage. She chose Manning, who promised he had an inheritance coming, but she maintained a "friendship" with O'Connor that many believe to have been sexual.
When it became clear that Frederick's inheritance was not forthcoming (he may have lied about that part), Marie hatched a plan with him to murder O'Connor and rob his house of everything they could find. She invited O'Connor to dinner one night and shot him in the back of the head. Frederick finished him off with a chisel. They then stashed his body in a hole they'd dug under the kitchen flagstones ahead of time and packed it with quicklime to speed up the body's decomposition.
Over the next two days, Marie gathered whatever valuables and stock certificates she could find at O'Connor's residence. Two of O'Connor's colleagues came to their house asking about him, so Marie and Frederick fled London. Marie went to Edinburgh, where she was arrested after trying to sell some of O'Connor's stock certificates.
The couple blamed each other at trial and both were found guilty and publicly executed in 1849. Their case was such a sensation that an estimated 50,000 people showed up to witness their deaths. One of those people was Charles Dickens, whose letter of disgust to The Times helped pave the way for the abolition of public executions in Britain.
Body Count: 1
Fate: Publicly hanged alongside her husband and accomplice. Marie became the inspiration for one of Dickens's characters, Hortense, the maid in his novel Bleak House.