I sort of appropriated this from a thread on Casebook...I hope SPE won't mind...but its a terrific post and one which should be read.

An unsolved murder is just that, unsolved. In not one of the 'Whitechapel' murder cases, from Smith in April 1888 to Coles in February 1891, was the offender identified although, obviously, there was more than one murderer at work. Where no hard evidence has been adduced, and no offender has confessed, it is not possible to positively identify a common hand for x, y, or z murders. That said certain facts should be obvious -

1. Each murder should be treated as an individual case and examined on its own merits.

2. No murder in the series should be assumed to have been committed by any particular suspect. That said it must be recognised that no hard evidence existed against any given contemporary suspect.

3. To treat a fixed number of that series of murders as having been committed by a common hand will influence all subsequent theorising and affect the conclusions reached.

To rigidly adhere to these criteria in a case with minimal evidence anyway, and for which no hard evidence is going to emerge at this remove in time, will prevent positive identification of any suspect, known or unknown.

Such ideas are unpopular with both the theorist and the fantasist - for they appear to stifle progress in seeking a solution to the case. And therein lies the rub - the case is incapable of solution.

So what are we left with? Only theorising, hypothesis and opinion I'm afraid. Accept it - it's a fact. We may certainly add to our peripheral and tangential knowledge and clear up minor mysteries in the case. Indeed, this has been the main thrust of Ripper studies for many years, certainly throughout the 'Internet years.'

Also it is possible internalise as much relevant information as is possible and to make informed and common sense deductions from what we have. From this we may arrive at our own, individual, conclusions. We may decide upon which of the murders have been committed by the Ripper, which of the known suspects is the most viable and which of the known facts are the most relevant and reliable. We may also decide what source material is the best. All this should be tempered by certain caveats.

1. No conclusion or opinion so arrived at is fact.

2. An open mind should be kept with regard to the conclusions and opinions reached and flexibility of thought that is receptive to new information and ideas.

3. Common sense and the rule of Ockham's Razor should prevail.

I have been accused in the past of being empirical and to a degree that may be true. Having been a police officer for nearly 30 years, and having studied this case for over 45 years, such influences cannot be ignored. For nearly all my working life evidence, law, and police procedure has been my bread and butter. But the greatest aid to any police officer (and as a tutor constable I personally instructed over 60 probationer constables) is common sense.

This all boils down to my own personal standpoint. First I fully accept that every individual has his or her own methods, ideas and preference for what they get out of the field of Ripper studies. I do not expect anyone to blindy accept what I say nor to think the way that I do. But personally speaking, and with regard to points raised above, I should like to finish by saying the following.

I do not like the term 'the canonical five' but I do agree that it has a certain 'convenience' when describing the five victims 'positively' identified by Macnaghten. In my opinion, based mainly on modus operandi, I believe that only Nichols, Chapman and Eddowes appear to be the common victims of a single killer. That does not mean that I reject Tabram, Stride and Kelly as Ripper victims, merely that the evidence in those cases is less compelling.

I have heard all the arguments over the years, all the debates, all the theories (daft and otherwise), all the hypotheses, &c. and I don't need some tyro to come along and tell me what is what. I have lost count of the times I have heard or read the ridiculous claim that 'Jack the Ripper' has been identified - all have fallen short of proof positive.

It is not boasting to say that I have the largest collection of Ripper books, files and material in the world (I am happy to hear from anyone who challenges that claim) and, therefore, almost all that is available I have to hand. I have tried to assist others working in the field whenever I can but this can become onerous. For years I have worked closely with Richard Whittington-Egan and Donald Rumbelow and have been encouraged, and advised, by my good friend Philip Sugden as well as the three pioneers of modern, more scholarly, Ripper research, Paul Begg, Martin Fido and my close friend Keith Skinner.

All that said, I am not an all-knowing Ripper oracle without peer and impervious to challenge. In fact, at times I grow quite sick of it all. Basically, I am a Ripper enthusiast (how I hate that word in this context) who happens to have written a few books on the subject - more by luck than judgement.

Finally a word on suspects. We shall never know who Jack the Ripper was. I am happy to state that as a fact. What we can do, though, is to read all that is available, listen to all the arguments for and against, and then reach our own personal opinion on who he most likely was or the sort of person that he was. Research will continue to produce more peripheral information that may influence these ideas and this is the biggest appeal and goal in 'Ripperology.'