“One of history’s oldest unsolved mysteries is the identity of Jack the Ripper, the infamous serial killer who stalked and murdered at least five women in London’s East End in 1888. The brutality of the Ripper’s crimes—as well as Scotland Yard’s failure to solve the case—caused a wave of hysteria in England and inspired gory headlines around the world. In one of the more recent efforts to crack the long-cold case, an Australian scientist used swabs from the stamps and seals of some of the letters Jack the Ripper was believed to have sent to police in order to construct a partial DNA profile of the sender. Though the results were admittedly inconclusive, they indicated that the samples were likely to have come from an unexpected source—a woman.

Far-fetched? Maybe not. It’s true that while many theories about the killer’s identity have emerged over the years, some of them more implausible than others (Lewis Carroll of “Alice in Wonderland” fame?), the police only had four actual suspects—all male. But after a witness said she saw the fifth Ripper victim, Mary Kelly, hours after she was murdered, the chief inspector in the case suggested it might have been the female killer escaping in Kelly’s clothing. Later proponents of this “Jill the Ripper” theory suggest that a midwife (possibly an abortionist) would have had the anatomical knowledge usually attributed to the Ripper, and would have had easy access to her female victims. As the theory goes, the most likely suspect may be Mary Pearcey, who was convicted and hanged in 1890 for the murder of her lover’s wife and child—and who had used a method similar to the Ripper’s to commit the crime.”

From: www.history.com