The notion that Jack the Ripper might not in fact be a man at all, but rather a woman, was one postulated by Inspector Abberline himself at the time of the killings. According to Donald McCormick, author of The Identity of Jack the Ripper published in 1959, Abberline raised the theory in a conversation with his mentor, Dr. Thomas Dutton after the murder of Mary Kelly. Testimony given by Caroline Maxwell, who lived in the area, was central to the argument.

The time of death for Mary Kelly was estimated to be between 3:30 and 4:00 A.M. on the morning of Friday, November 9th 1888. This time seems fit not only due to medical evidence such as temperature of the body and stiffness of the joints, but correlates as well with the majority of the testimony given by those who claim to have either seen or heard her the night of her death. Majority, however, does not include the testimony of Mrs. Caroline Maxwell.

Mrs. Maxwell testified to have seen Mary Kelly not once but twice several hours after doctors believe she had died. The first occassion was between 8:00 and 8:30 A.M. in front of Miller's Court, looking, in Mrs. Maxwell's opinion, to be quite ill. Mrs. Maxwell stated that she was sure of the time because her husband returned from work around 8:00 each morning. The second time was an hour later when Mrs. Maxwell claims she saw Kelly speaking with a man outside the Britannia public house.

Mrs. Maxwell vividly described the clothes she saw on the woman she believed to be Kelly that morning as "a dark shirt, velvet bodice and a maroon-coloured shawl." When asked if she had ever seen Kelly in this outfit, she replied that she definitely remembered her wearing the shawl.

Abberline had no reason to distrust this witness, and she continued to adamantly adhere to the times and descriptions she had given. The problem perplexed him, and he later approached Dutton about it, asking, "Do you think it coukld be a case not of Jack the Ripper but Jill the Ripper?" Abberline based the brunt of the argument on the fact that it was possible that the killer dressed up in Kelly's clothes in order to disguise herself, therefore accounting for Mrs. Maxwell's sighting of her the next day.

Dutton answered that he believed it was doubtful, but that if it were a woman committing the crimes, the only kind capable of doing so would be a midwife.

Thus begins the theory of Jill the Ripper -- sometimes labeled the mad midwife. As ludicrous as it may sound initially, there are several points which add credibility to the theory. First, the fact that all of London was looking for Jack the Ripper (i.e. a man) would allow a female murderer to walk the streets of Whitechapel with considerably less fear of capture or discovery. Second, a midwife would be perfectly common to be seen at all hours of the night. Third, any presence of blood on her clothing would be immediately discarded as a result of her work. Finally, based on the evidence pointing to an anatomically educated murderer, a midwife would have the anatomical knowledge some believed the murderer possessed.

William Stewart was one of the first to write about the possibility of Jill the Ripper in his book Jack the Ripper: A New Theory, published in 1939. In it, he attempted to narrow down not the identity of the killer but the class of person he might have been by asking four pertinant questions:

1. What sort of person was it that could move about at night without arousing the suspicions of his own household or of other people that he might have met.

2. Who could walk through the streets in blood stained clothing without arousing too much comment.

3. Who would have had the elementary knowledge and skill to have committed the mutilations.

4. Who could have been found by the body and yet given a satisfactory alibi for being there.

Stewart's prime candidate, in following with the conversation between Abberline and Dutton over fifty years before, was that the killer had been a midwife -- possibly an abortionist. He postulates that "she might have been betrayed by a married woman whom she had tried to help, and sent to prison -- as a result, this was her way of recenging herself on her own sex."

Stewart mentioned the aforementioned amenities of the theory (anatomic knowledge, reason to be bloodstained, et alia) in order to back up the assertion.

Specifically, Stewart seems to have been focused on the fact that a midwife would have been able to "almost instantly produce unconsciousness, particularly in persons given to drink, by a method frequently used on patients in those days by midwives who practised among the extremely poor." In other words it is suggested that midwives found it common practise to knock out their patients by exerting pressure on the pressure points.

Mainly, however, Stewart banks on the fact that Mary Kelly was three months pregnant at the time of her death. She could barely afford her lodgings, let alone a baby, so, according to Stewart, she decided to terminate her pregnancy. He claims that the murderer was called in to abort the baby and killed Kelly once she was admitted into the room, later burning her bloodsoaked clothing in the grate and escaping wearing Kelly's clothing.

This is important, because it explains the sighting by Mrs. Maxwell at 8:00 the next morning -- she could possibly have seen the midwife/abortionist in Kelly's garb: the shawl of which she remembered to have been worn by Kelly.

Stewart provides other points which suggest that the murderer was a woman. First he claims that Nichols' bonnet, which she had mentioned in her now famous line to her landlord: "I'll soon get my doss money, see what a jolly bonnet I've got now," was given to her by the mad midwife as a gift. He claims that if a man had given it to her, she would have boasted of the fact.

Also, Stewart asserts that Chapman's pockets were turned inside out because inside was held incriminating evidence which could have identified her as the murderer. After the contents were disarranged at the victim's feet, the midwife decided to arrange them cryptically in order to throw off the police.

In answer to the question of why the midwife would remove organs from her victims, Stewart claimed that she would have the sufficient anatomical knowledge to do so and that it was an obvious ploy to direct attention away from her. He noted, "the particular mutilations practised by the killer held a psychological fascination and horror for all women, and as a result physiological reactions took place among women and in places remote from the scenes of the murders."

Stewart also believes his theory explains the reason why Mary Kelly was unclothed and her clothes were neatly folded on a nearby chair -- the prostitute had stripped for a routine medical abortion from the midwife she had contracted. Hence, the midwife struck upon her unsuspecting victim.