Reply #19: Here's John Douglas's take on it (from Wiki)

[Jmaxfie1]

David Cohen (1865–1889) was a Polish Jew whose incarceration at Colney Hatch Lunatic Asylum roughly coincided with the end of the murders. Described as violently antisocial, the poor East End local was suggested as a suspect by author and Ripperologist Martin Fido in his book The Crimes, Detection and Death of Jack the Ripper (1987). Fido claimed that the name "David Cohen" was used at the time to refer to a Jewish immigrant who either could not be positively identified or whose name was too difficult for police to spell, in the same fashion that "John Doe" is used in the United States today.<76> Fido identified Cohen with "Leather Apron" (see John Pizer above), and speculated that Cohen's true identity was Nathan Kaminsky, a bootmaker living in Whitechapel who had been treated at one time for syphilis and who could not be traced after mid-1888—the same time that Cohen appeared.<77> Fido believed that police officials confused the name Kaminsky with Kosminski, resulting in the wrong man coming under suspicion (see Aaron Kosminski above). Cohen exhibited violent, destructive tendencies while at the asylum, and had to be restrained. He died at the asylum in October 1889.<78> In his book The Cases That Haunt Us, former FBI criminal profiler John Douglas has asserted that behavioural clues gathered from the murders all point to a person "known to the police as David Cohen ... or someone very much like him".<79>