The origins of the murders in Whitechapel, made it a lot more difficult for the police to work: at this period in time, the public generally did not like the police due to the fact they had not been around long and had suddenly come into a lot of power.
The tension between groups made it much more difficult for the police and the busy working streets also washed away a lot of evidence. Due to the circumstances of the time, the police did the best they could apart from not cooperating with each other (e.g.
washing away the chalk writing.) They had unfortunate circumstances such as the place of the murders and lack of technology to help them through the investigation.
By leaving no clues or evidence, and working quickly (e.g.
double murder with Elizabeth Stride and Catherine Eddowes.) Suspects were investigated but often they had alibis or no connections at all.
Police had no experience of this type of killer before..to this degree, which had a knock on effect regarding organisation and investigation. It would be like me blaming you for not knowing the answer to the question you have just asked. Not only is it hard even today to catch a suspect, it is even harder to prove it.
I suggest you read this dissertation Brian Schoeneman. Many murder investigations take a year after the suspect is in custody to complete.
Also in 1888, it was a chance for the police to prove their worth.
They had been given a job and it appeared they were not doing it very well.
Although officers were told to patrol the streets for at least 14 hours of a day, it was still extremely hard to prevent crimes due to the old winding streets in the big city.
One place that was extremely difficult to police was the slum of the east end, Whitechapel.