Dr. Cohn/ Dr. Koch

Lewis Keaton joined the Metropolitan Police in 1891, three years after the Whitechapel murders. In 1969, just before he died in his 100th year, he gave a recorded interview in which he identified the killer as a doctor and gave his name as Cohn, Koch or something similar. He attributes to the doctor the motive of obtaining specimens of uteri infected with venereal disease for research purposes.
In the 1891 census there are 28 males of adult age listed in London with the surname Cohn. For the same area and period there are 22 listings under the surname Koch. Of these one Cohn entry was a doctor. There was no Koch entry listed as a physician, but there was one individual with medical connections.
The doctor in question is listed as Dr. De Cohn and was in 1891 staying at the Royal Hotel, Bridewell, London. He is described as a visitor, a married man, 38 years of age and born in Germany. His profession is listed simply as "Physician."
The Koch entry with medical connection is one Heinrich Koch who is described as a ward attendant at the Hackney District German Hospital. His age is given as 57 years old.
There is what may be a correlation between one of the "non medical" Koch entries from 1891 with a Dr. Koch listed in 1901. In 1891 there is an entry for John G. Koch, aged 36, whose profession is given as a "demarcation officer." He was at the time living in Penge and was born in Ceylon (now Sri Lanka.) The combination of Penge and Ceylon is an unusual one but is replicated in the 1901 entry for a Dr. Wilfred Koch. His details are given as follows:
7 Haysleigh Gardens, Penge, Kent
Wilfred Koch
Aged 38
Doctor of Medicine
Born in Ceylon.
I would suggest that the extremely unlikely combination of an unusual surname, Koch, residence in Penge, birth in Ceylon and a medical connection make for a strong possibility of a family connection between Heinrich in 1891 and Wilfred in 1901. I have not been able to trace Wilfred Koch in the 1891 data.
We must bear two things in mind. The name Cohn/Koch was derived from oral data (a taped interview) of poor quality. There are many other possibilities. If, for example, Keaton said that the doctor's name was not Cohn but Cohen then many more possible candidates would be put into the frame. Also in his interview Keaton stated that this doctor used strychnine. This suggests that Keaton may have been introducing elements from other cases - the name of Dr. Cream springs most readily to mind. Cream was about his murderous work in 1891 and 1892, the very time when Keaton joined the force and the case made the headlines to such an extent that he must have been aware of the details of it.