Was Aaron Kosminski Jack the Ripper?

The Macnaghten Memorandum and the Swanson Marginalia

The first time any Jack the Ripper suspects were officially named was in the Macnaghten Memorandum, written in 1894 by Sir Melville Macnaghten, the Chief Constable of the Metropolitan Police. It was an internal memo which wasn’t made public at the time, only emerging several decades later. This memorandum was created in response to an 1894 article in the Sun newspaper about a suspect called Thomas Cutbush who was in Broadmoor Lunatic Asylum. Macnaghten wanted to set the record straight, although author A.P. Wolf later suggested that he wrote it to protect police superintendent Charles Cutbush, who was supposedly Thomas Cutbush’s uncle.

“No one ever saw the Whitechapel murderer; many homicidal maniacs were suspected, but no shadow of proof could be thrown on anyone. I may mention the cases of 3 men, any one of whom would have been more likely than Cutbush to have committed this series of murders:

(1) A Mr M. J. Druitt, said to be a doctor and of good family — who disappeared at the time of the Miller’s Court murder, and whose body (which was said to have been upwards of a month in the water) was found in the Thames on 31st December — about 7 weeks after that murder. He was sexually insane and from private information I have little doubt that his own family believed him to have been the murderer.

(2) Kosminski — a Polish Jew – and resident in Whitechapel. This man became insane owing to many years’ indulgence in solitary vices. He had a great hatred of women, especially of the prostitute class, and had strong homicidal tendencies: he was removed to a lunatic asylum about March 1889. There were many circumstances connected with this man which made him a strong suspect.

(3) Michael Ostrog, a Russian doctor and a convict, who was subsequently detained in a lunatic asylum as a homicidal maniac. This man’s antecedents were of the worst possible type, and his whereabouts at the time of the murders could never be ascertained.” – Sir Melville Macnaghten

As Kosminski was one of the suspects named by Macnaghten, some Ripper historians regard him as credible candidate. Supporting this view are the notes found in the margins of Dr Robert Anderson’s 1910 book, The Lighter Side of My Official Life. While Anderson didn’t directly name his favoured suspect, he made it clear that he believed the Ripper was a Polish Jew.

Dr Robert Anderson, formerly a barrister, was appointed Assistant Commissioner of the Metropolitan Police and head of the Criminal Investigation Department on 1 September 1888, the day after the murder of Polly Nichols, and was one of the highest-ranking officers involved in the investigation.

In his book, Anderson wrote:

“One did not need to be a Sherlock Holmes to discover that the criminal was a sexual maniac; that he was living in the immediate vicinity of the scenes of the murders; and that, if he was not living alone, his people knew of his guilt, and refused to give him up to justice. During my absence abroad the Police had made a house-to-house search for him, investigating the case of every man in the district whose circumstances were such that he could go and come and get rid of his bloodstains in secret. The conclusion we came to was that he and his people were certain low-class Polish Jews; for it is a remarkable fact that people of that class in the East End will not give up one of their number to Gentile justice.”

He went on to state,

“the only person who ever had a good view of the murderer unhesitatingly identified the suspect the instant he was confronted with him; but he refused to give evidence against him. In saying that he was a Polish Jew I am merely stating a definitely ascertained fact.”

The plot thickened in 1981, when the grandson of Chief Inspector Donald Swanson discovered a copy of Sir Anderson’s book in his late grandfather’s collection, which contained notes in the margins made by Swanson over 60 years earlier. These annotations have since become known as the ‘marginalia’. Swanson had been given overall responsibility for the Whitechapel investigation in September 1888, while Robert Anderson was on sick leave.

Beneath the section describing the witness’s reluctance to identify the killer, Swanson had scribbled:

“As to why the witness wouldn’t give evidence… because the suspect was also a Jew, and witness would be the means of murderer being hanged, which he did not wish to be left on his mind.”

More damningly still, he added some further observations about the suspect being identified at the Seaside Home. He wrote:

‘On suspect’s return to his brother’s house in Whitechapel, he was watched by police day and night. In a very short time, the suspect, with his hands tied behind his back, went to Stepney Workhouse and then to Colney Hatch, and died shortly afterwards. Kosminski was the suspect.”

The identity of the Seaside Home witness remains uncertain, although I explore this in more detail in episodes 5 and 7 of my Jack the Ripper series. However, Swanson’s marginalia does confirm that the witness was Jewish and that he recognised the killer as also being a Jew.

The marginalia prompted historian Martin Fido to inspect the Colney Hatch asylum records to see if he could locate an inmate with the name Kosminski. He found one – 25-year-old hairdresser Aaron Kosminski, who had arrived at Colney Hatch on 7 February 1891.

Who Was Aaron Kosminski?

Aaron Mordke Kosminski was born on 11 September 1865, making him 23 at the time of the killings. The youngest of seven siblings, he had two older brothers, Isaac and Wolf, and four sisters. Their father, Abram Josef Kosminski, worked as a tailor. Aaron was born in Klodawa, a town that is now in Poland but was then part of the Russian Empire. After 1881, Jews across the Empire were scapegoated for the assassination of Tsar Alexander II, despite the assassin not being Jewish. The widespread anti-Semitic violence led to the migration of tens of thousands of Jews from across Eastern Europe, many of them settling in London. The Kosminski family did not travel together, with Aaron’s older brothers arriving first. We know little about Aaron’s early life, but he was a teenager by the time he arrived in London, by which point his father Abram had died. The eldest son, Isaac, followed in his father’s footsteps and became a tailor, and the family moved frequently around the East End, living at various addresses over the years. At the time of the Ripper murders, Aaron was living with Isaac, and his medical records described him as a hairdresser by trade, though he had not worked for several years.

Dog-muzzling court case

In December 1889, Aaron Kosminski was summoned to Guildhall Police Court and fined for allowing an unmuzzled dog to roam in a public thoroughfare – Metropolitan Police Commissioner Sir Charles Warren had enacted laws requiring all dogs in London to be muzzled or kept on a lead, to address the city’s growing stray dog problem which had led to many people being bitten. Kosminski denied owning the dog and refused to pay the fine on the Sabbath but agreed to return the following Monday to pay the 10-shilling penalty. During the proceedings, confusion arose when Aaron’s brother, who accompanied him to court, gave their family name as Abrahams, though he eventually admitted it was Kosminski. This suggests the family may have adopted the more anglicised name Abrahams in an effort to integrate into their new community.

Mental Illness and Asylum Records

The following year, on 12 July 1890, Aaron Kosminski was admitted to the Mile End Old Town Workhouse Infirmary, with the official reason listed as ‘two years insane’. Jacob Cohen, a business partner of Aaron’s brother, Wolf, reported that, ‘He goes about the streets and picks up bits of bread out of the gutter and eats them, he drinks water from the tap, and he refuses food at the hands of others. He took up a knife and threatened the life of his sister. He is very dirty and will not be washed. He has not attempted any kind of work for years.’ After three days at the workhouse, Aaron was discharged into his brother’s care at 16 Greenfield Street, just off Commercial Road, but was readmitted to the Workhouse Infirmary just over six months later, in February 1891. He was aged 25 at the time, although the admission book states his age as 26. Three days later, on 7 February 1891, he was transferred to the Middlesex County Lunatic Asylum at Colney Hatch. The admission notes confirmed he did not pose a danger to others, but said, ‘He declares that he is guided and his movements altogether controlled by an instinct that informs his mind. He says he knows the movements of all mankind, he refuses food from others because he is told to do so, and he eats out of the gutter for the same reason.’ The cause of this behaviour was initially listed as ‘unknown’ but later changed to ‘self-abuse’ – a term used in the Victorian era to refer to masturbation, which was believed not only to be sinful, but to cause physical and mental health problems.

While at Colney Hatch, Aaron Kosminski was described as ‘deluded, apathetic, and morose’, while another account explained that he was difficult to manage due to his delusions and his refusal to be bathed. By January 1892, reports stated that he was ‘incoherent, at times excited and violent’, and that he had attempted to hit an attendant with a chair. Despite this, he often appeared lethargic and refused to take part in activities to pass the time. At the age of 28, Aaron was transferred to Leavesden Asylum in Hertfordshire, where he remained largely uncommunicative. Surviving records from Leavesden are scarce, but one from 1912 noted, ‘no replies can be got; dull and stupid in manner and faulty in his habits. Requires constant attention’. By 1914, however, there seemed to be a shift in his condition, as he was described as ‘incoherent and excitable: troublesome at times. Hallucinations of hearing. Untidy.’ Aaron Kosminski died at Leavesden on 24 March 1919, aged 53.

The Case for Aaron Kosminski as Jack the Ripper

Overall, our knowledge of Aaron Kosminski and his life is limited, with his credibility as a suspect mainly coming from his inclusion in the Macnaghten Memorandum, Swanson’s marginalia, the fact he was a Polish Jew, and that he was committed to an asylum less than 2 and a half years after the last canonical murder. But is this enough? Let’s look at some of the arguments against his Jack the Ripper candidacy.

The Case Against Aaron Kosminski

It should be remembered that Melville Macnaghten was not directly involved in the canonical 5 murders. At the time, he was managing his father’s tea plantation in India and had no prior law enforcement experience until he was appointed Assistant Chief Constable of the Met Police in 1889. This raises questions about his familiarity with the case. Additionally, Macnaghten’s own favourite suspect was in fact Montague Druitt.

There’s also some inconsistencies in Macnaghten’s description of Kosminski. For example, he said, ‘He had a great hatred of women, especially of the prostitute class, and had strong homicidal tendencies: he was removed to a lunatic asylum about March 1889’.

However, nothing in Kosminski’s records suggests he hated women or prostitutes, and his asylum records indicate that he wasn’t considered dangerous, with only one notable incident where he tried to hit an attendant with a chair. He was not admitted in March 1889 – instead, he went first to the workhouse infirmary in 1890, and then to the asylum in February 1891. That said, Macnaghten wrote his memorandum some years after the events, so he may have made a mistake. The lack of evidence from Kosminski’s Colney Hatch records isn’t necessarily conclusive, as historical records are often incomplete and can be lost over time.

As for the Swanson marginalia, critics have pointed out that the section containing the key phrase ‘Kosminski was the suspect’ was jotted down in a different pencil and may have been added to the marginalia at a later date, by which time his memory may have been less accurate. Nobody knows the reason for his writing these notes. According to Swanson’s annotations, the suspect died shortly after admission to Colney Hatch, but in reality, Kosminski lived for many more years, dying at Leavesden in 1919. This discrepancy cannot easily be explained away as a result of faulty memory, because Swanson had already stated in a Pall Mall Gazette article as early as May 1895 that he believed the Ripper was dead – long before he wrote the marginalia.

In September 1946, the Reynolds News published an extract from City of London Detective Robert Sagar’s memoirs, which read:

“We had good reason to suspect a man who worked in Butcher’s Row, Aldgate. We watched him carefully. There was no doubt that this man was insane, and after a time his friends thought it advisable to have him removed to a private asylum. After he was removed, there were no more Ripper atrocities.”

Kosminski was a hairdresser, not a butcher, and Colney Hatch was not a private asylum. Sagar’s account aligns with documentation from Detective Inspector Harry Cox, who wrote in 1906 that he had been involved in the surveillance of a Jewish suspect for three months after the Mary Jane Kelly murder. Cox stated that this suspect owned a business in the East End, and alleged that his motive was revenge, as he had been “wronged by a woman of the lower classes”. He also noted that this suspect had spent time in a Surrey asylum and was known to take walks at night, with no further murders occurring because he knew he was being watched. The accounts of Sagar and Cox agree on some points, so we can be confident that a suspect in Aldgate was indeed under surveillance, but the description of the man they were pursuing does not match Kosminski. In fact, it more closely aligns with Jewish butcher Jacob Levy, who I discussed in a recent episode.

An AI-generated image supposedly depicting Aaron Kosminski was recently created based on eyewitness descriptions of people seen with the victims shortly before their deaths, but as any Ripper historian will tell you, many of these descriptions were contradictory and unreliable. Regardless of what Kosminski’s physical appearance may have been – something we have no concrete evidence for – it was said that he primarily spoke Yiddish and had a limited grasp of English, which would have made him more recognisable as Jewish. Given the anti-Semitic feeling at the time and the growing panic caused by the brutal murders and mutilations, it seems less likely that Kosminski could have easily lured prostitutes into dark corners, compared to someone who could blend in more seamlessly with native Londoners.

Nathan Kaminski

In an intriguing twist, the inconsistencies in the Swanson marginalia led Martin Fido to propose a compelling new theory: that Swanson had been mistaken when he wrote the name Kosminski, and was actually referring to another Polish Jew named Nathan Kaminski, alias David Cohen. Kaminski had been at Colney Hatch asylum, and the dates of his incarceration matched Macnaghten’s report much more closely than those of Aaron Kosminski. Nathan Kaminski died in 1889, which matched Donald Swanson’s statement that the suspect died shortly after being sent to Colney Hatch. This was true for Nathan Kaminski, but not for Aaron Kosminski.

We know very little about Kaminski aside from his year of birth, which incidentally was 1865, like Aaron Kosminski. He lived at 15 Black Lion Yard and was admitted to the Whitechapel Workhouse Infirmary on 24 March 1888 suffering from syphilis and was discharged as cured six weeks later. On the face of it, Kaminski might even be a stronger suspect than Kosminski, as the dates are more consistent and his syphilis diagnosis could be evidence that he visited prostitutes. Is it possible that all this time, Ripperologists have been chasing the wrong man due to a misspelling of his name?

The DNA Evidence and the Eddowes Shawl

About 100 years after the final Jack the Ripper murder, an unexpected discovery emerged which promised to cast new light on the enigma. This fresh evidence seemed to suggest that Aaron Kosminski might be the murderer after all, despite the contradictions and the lack of evidence of violent tendencies.

Russell Edwards and the DNA Claims

In 2007, businessman and author Russell Edwards purchased a shawl at an auction, which had a colourful history. The shawl was nine feet long and made of a silky fabric with tassels and a floral design, prompting some to suggest it was a table runner rather than an item of clothing. It bore several stains and had previously been traced to an Essex antiques dealer by Ripper researcher Paul Harrison in 1989. Between then and its 2007 purchase by Edwards, it had been loaned to Scotland Yard’s Black Museum and displayed at a 2001 Jack the Ripper conference in Bournemouth, where it was handled by numerous attendees. The antiques dealer had cut out a piece of the garment, as had Scotland Yard’s crime museum, although they declined to exhibit it as they were unconvinced of its authenticity. Given the amount of handling, transportation, and storage it had gone through, any DNA on the shawl was likely to be heavily contaminated.

But what made this shawl so special that it attracted so much attention? It was claimed that it belonged to Catherine Eddowes and had been found at the scene of her murder in Mitre Square in 1888. The story went that a 41-year-old Acting Sergeant from the Metropolitan Police’s N Division, named Amos Simpson, took the shawl as a souvenir after accompanying the body to the mortuary. This is an unusual tale for a couple of reasons: first, Simpson was usually stationed in Cheshunt, Hertfordshire, and second, the murder occurred within the City of London jurisdiction, making it unlikely that a City detective would have given such a crucial piece of evidence to Simpson. There’s also no record of Amos Simpson being present at the crime scene, and the official inventory of Eddowes’ possessions does not mention any such shawl.

After purchasing the shawl, Russell Edwards hired Finnish forensic geneticist Dr Jari Louhelainen to analyse the stains on the shawl at Liverpool John Moores University. Louhelainen discovered that some of the stains were blood, while others were possibly semen. However, due to the degradation of the material, the tests were challenging, and Louhelainen had to develop a new technique to extract and amplify the minuscule samples. Meanwhile, Edwards traced Karen Miller, a descendant of Catherine Eddowes, as well as a female descendent of Aaron Kosminski’s sister, and both provided DNA samples for comparison.

In September 2014, Edwards published his sensational book, ‘Naming Jack the Ripper’, in which he claimed that Karen Miller’s DNA matched the blood on the shawl, a match shared by only 1 in 290,000 people worldwide. He also revealed that the sample from Kosminski’s descendant was a 100% match with the semen on the shawl.

Criticism of the DNA Evidence

But if the evidence was so clear-cut, why hasn’t Aaron Kosminski been officially identified as Jack the Ripper, and the case closed once and for all? Aside from the provenance of the shawl and the inevitable contamination over the years, many scientists have strongly criticised the findings. One of the main issues is that only mitochondria DNA was available for testing, as it lasts longer than nuclear DNA. However, mitochondrial DNA, or MtDNA, has a major limitation – it’s typically used for exclusion rather than definitive identification. MtDNA is passed down through the maternal line, and unlike nuclear DNA, it cannot distinguish between individuals who share the same ancestry. Hansi Weissensteiner, a mitochondrial DNA expert from Innsbruck University, points out that thousands of other people could potentially share the same MtDNA, making it an unreliable marker for identifying a specific individual.

Geneticist Alec Jeffreys, who is considered the father of the genetic fingerprinting and DNA profiling techniques widely used today, expressed scepticism about the findings, saying that they ‘need to be subject to peer review, with detailed analysis of the provenance of the shawl and the nature of the claimed DNA match with the perpetrator’s descendants and its power of discrimination. No actual evidence has yet been provided.’

In 2019, five years after the book was released, Dr Louhelainen finally published a paper for peer review in the journal of Forensic Sciences. One significant point of contention was that the genetic sequences of the living relatives of Eddowes and Kosminski were not published transparently.

In August 2024, the Journal of Forensic Sciences issued a formal expression of concern, noting that questions had been raised after publication. When the Editor-in-Chief attempted to obtain the original raw data from the authors, Edwards and Louhelainen had been unable to provide it, citing instrument data failure and other complications. As a result, no determination could be made about the validity of the findings.

In February 2025, some media outlets enthusiastically announced that Jack the Ripper had been officially identified but doubts quickly surfaced. Journalists soon revised their initial headlines, rephrasing their articles more cautiously to state that Aaron Kosminski was ‘possibly’ the Ripper. Author Hallie Rubenhold also criticised the continuing interest in the shawl, saying, ‘How this story about the DNA on the so-called Eddowes shawl is still in the headlines baffles me. It’s been debunked numerous times by scientists. There is no historical evidence, no documentation that links this shawl to Kate Eddowes. This is history at its worst.’

Could the Shawl Have Come from Another Source?

Could there be any truth in the claims about the shawl? Sotheby’s Auction House examined it and concluded it was likely made in the early 1900s, with the possibility that it could be a little older, potentially putting it around the right age. One possible explanation for why the shawl didn’t appear in the police inventory is that it might not have belonged to Catherine Eddowes or the killer. It’s conceivable that the shawl was used to cover Eddowes’ body out of respect until the police arrived. This could have been done by someone like the nightwatchman from the Kearley & Tonge warehouse, or Richard Pearce, a City of London policeman who lived nearby and was among the first on the scene. If so, Eddowes’ and the killer’s DNA could have been transferred to it, then at the mortuary, Amos Simpson could have taken it as a souvenir, as it was deemed unimportant to the investigation.

Karen Miller, the three-times great granddaughter of Catherine Eddowes, has called for a new inquest to be opened by Britain’s High Court to formally name Kosminski as the killer, but unless things change in the future, it seems unlikely her request will be granted.

The mystery will likely remain unsolved unless further evidence comes to light, or scientists can definitively confirm or disprove the claims.

Prash Ganendran

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