Notes in margin of book 'solve Ripper's identity'
The Metropolitan Police officer wrote that Kosminski was identified as the Ripper by a witness but because the suspect was insane he could not be questioned. The detective added the witness refused to testify against Kosminski and speculated that was because he was a fellow Jew and did not want him to hang.
But, despite the strong views held by the officer, Chief Inspector Donald Swanson, who arguably had the best overview of the murder investigation, Ripper specialists and historians have cast doubt on Kosminiski as a likely suspect.
The details of the Polish immigrant, who came to Britain in about 1882, are part of the vast industry built up around identifying the notorious killer.
The murderer terrorised residents in the White-chapel area of east London during 1888 when at least five women prostitutes were murdered and their bodies mutilated.
Debate over who was responsible for the crimes was reignited yesterday at the relaunch of the Met's crime museum, which is not open to the public.
One of the new exhibits is a book, called The Lighter Side of My Official Life, the memoirs of Dr Robert Anderson, who was an assistant commissioner at Scotland Yard at the time of the Ripper investigation. The book was handed down through Swanson's family.
Swanson names Kosminski in handwritten notes in that book, which are in the margins, across the bottom of the page and on blank pages inside the book.
Swanson's notes, which have been known about since the 1980s, provide some of best clues to the Ripper's identity.
Kosminski came to the attention of police after threatening his sister with a knife. Although he was soon identified as a possible suspect in the Ripper investigation, his insanity meant he could not be formally questioned and he was taken instead to the Metropolitan Police convalescent home in Brighton where he was put through an unofficial identity parade. The only alleged witness to any of the Ripper murders - believed to be a man named Israel Schwartz - picked him out.
Kosminski ended up in a workhouse in Stepney, east London, and then an asylum in Colney Hatch. He died in 1919.
Swanson's notes read: "After the suspect had been identified at the seaside home where he had been sent by us with difficulty in order to subject him to identification, and he knew he was identified. On suspect's return to his brother's house in Whitechapel he was watched by police (City CID) by day and night. In a very short time, the suspect, with his hands tied behind his back, was sent to Stepney Workhouse and then to Colney Hatch and died shortly afterwards - Kosminski was the suspect-DSS."
Swanson added: "And after this identification which suspect knew, no other murder of this kind took place in London."
As there is no surviving forensic evidence from the case, it is impossible for detectives to prove the identity of Jack the Ripper.
Some Ripper experts downplay the significance of Kosminski. They argue that his insanity took the form of auditory hallucinations, a paranoid fear of being fed by other people, and a refusal to wash or bathe. They say he was described as harmless in the asylum and his inclusion as a suspect was more the result of anti-Semitism.
Keith Skinner, a historical researcher who has written extensively about the Ripper case, concluded yesterday: "The Swanson marginalia produces as many questions as it does answers."