According to Melville Macnaghten in his 1894 Memoranda one of the three men who was more likely than Thomas Cutbush to have been Jack the Ripper was "Kosminski" who, according to Macnaghten, was:-
...a Polish Jew, & 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, & had strong homicidal tendencies; he was removed to a lunatic asylum about March 1889..."
Kosminski is of particular interest because, in addition to Macnaghten, the two highest ranking officers, with direct responsibility for the Jack the Ripper investigation, also considered him the to be a strong suspect for the Jack the Ripper murders.
In 1910 Sir Robert Anderson, Assistant Commissioner throughout the murders, wrote in his memoirs that:-
...undiscovered murders are rare in London, and the "Jack-the-Ripper" crimes are not in that category...I will merely add that the only person who had 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..."
Although Anderson didn't name this suspect, it is apparent that he was referring to Macnaghten's "Kosminski," a fact confirmed in 1987 when Chief Inspector Donald Swanson's copy of Anderson's memoir was made public.
Swanson was the officer tasked with assessing all the information on the Jack the Ripper case, and few people possessed anything like his comprehensive knowledge of the murders.
He and Anderson became firm friends and when Anderson's memoir - entitled The Lighter Side of My Official Life - was published, Swanson received his own personally inscribed copy.
Swanson made penciled annotations to Anderson's narrative, and in so doing provided a little more information.
Where Anderson talks of a witness "unhesitatingly" identifying their suspect but refusing to give evidence against him, Swanson explains that this was "...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..."
He goes on to say that, following this identification, the suspect was returned to his brother's house in Whitechapel where the City Police kept him under constant surveillance.
A short time later this suspect was taken to Stepney Workhouse and from there he was sent to Colney Hatch lunatic asylum where, according to Swanson, he died shortly afterwards.
Swanson ends with the emphatic statement that "Kosminski was the suspect."
It is now known that the suspect in question was a man named Aaron Kosminski, a feeble minded imbecile, who was admitted to Colney Hatch Asylum in February 1891, but who had begun displaying signs of insanity at some stage in the late 1880's.
He believed that a higher power spoke to him, and controlled his actions, and claimed to know the movements of all mankind. He refused to wash and would not accept food from others, preferring instead to eat from the gutter.
Schizophrenic, delusional, paranoid and incoherent are all characteristics displayed by Aaron Kosminski.
But there are numerous arguments against his having been Jack the Ripper.
Swanson, apparently new little about his fate, as Kosminski didn't, as Swanson claimed, die shortly after being admitted to Colney Hatch asylum. In fact he lived for many years, transferring to Leavesden Asylum in 1894, where he died in 1919.
Throughout the entire period of his confinement Aaron Kosminski was never classed as homicidal, and it is specifically stated in his records, that he was not a danger to others.
Some of his notes state that he was excitable, but the only mention of his being violent was that he once grabbed a chair and made to strike an attendant with it.
Anderson and Swanson were the two highest ranking officers with direct responsibility for the Ripper investigation, and they were both in a position to know the evidence against all the suspects.
Yet, unless they are referring to a different Kosminski, or there is more information about him that has yet to come to light, there is little evidence to link Aaron Kosminski to the Jack the Ripper murders.