Mary Pearcey, like many other famous Victorian-era murderers, has been suggested as a suspect in the Jack the Ripper slayings. She was apparently the only female suspect mentioned at the time. Sir Arthur Conan Doyle, creator of Sherlock Holmes, speculated at the time that the Ripper might have been female, as a woman could have pretended to be a midwife and be seen in public in bloody clothing without arousing suspicion or notice.

This theory was then expanded upon in 1939 by William Stewart in his book Jack the Ripper: A New Theory, which specifically named Pearcey in connection with the crimes. All evidence given is circumstantial, and there is no physical evidence or eyewitness reports linking Pearcey to the Ripper crimes.

F. Tennyson Jesse, the British criminal historian, explained the theory in her study of Pearcey’s case: “It was no wonder that, simultaneously with the discovery of the crime, legends should have sprung up around her figure. The rumour even arose that the notorious Jack the Ripper had been at work in the locality, and though this was quickly disproved, yet the violence and horror associated with the crime was such as to make it understandable how the rumour arose in the first place. Even in the earliest paragraphs which announced the discovery of the crime, several false statements were suggested.”

In May 2006, DNA testing of saliva on stamps affixed to letters allegedly sent by Jack the Ripper to London newspapers, and thought by some modern writers to be genuine, appeared to come from a woman. This led to extensive discussion of Pearcey and her crime in the global press.