In the 2002 book Portrait of a Killer: Jack the Ripper Case Closed, Patricia Cornwell declared that her conclusion was , after much detailed research, that Walter Sickert was JTR. This was not an original idea, his name had been associated with the mystery for many years. It wasn't even the first publication on the subject. In her 1990 book, Sickert and the Ripper Crimes, Jean Overton Fuller asserted that he was indeed the infamous serial killer. Earlier still, in 1976, Stephen Knight in his book Jack the Ripper: The Final Solution put forward the theory that Sickert was an unwilling accomplice to the real Jack.
Now we have a new real Jack the Ripper, well not exactly new. This one has been on the Ripper list since the time of the murders. In yet another book on the subject, Russell Edwards (no relation) names Aaron Kosminski as quite definitely, without any doubt, the real thing. Based on the DNA profiling of samples of blood on a shawl said to have belonged to, or have been associated with Catherine Eddowes who was believed to have been the Ripper's fourth victim (and the second to die under his hand during the infamous double event of Sunday 30th September 1888).
I am, of course, not qualified to comment on the accuracy of DNA results although it does seem fairly obvious that they wouldn't stand up in a court of law (not that that is relevant here). Firstly, the shawl was obtained under what would now be considered very dubious circumstances. Apparently, a policeman took, or was given it, once it was considered to be no longer important to the investigation, to give to his wife. Although why anyone would give a bloodstained shawl as a gift to his nearest and dearest is beyond me.
Secondly, even though it survived and remained in the hands of the same family for all of these years it can hardly be claimed to have been kept in a sterile and uncontaminated condition. Nevertheless, DNA testing appears to show that the shawl was stained with the blood of both Eddowes and Kosminski (comparisons were made with samples donated by present day members of the two bloodlines). It seems to me that without some other supporting evidence, the best that can be said to explain this is that at some time Kosminski came into contact with both Eddowes and the shawl. Given that Eddowes was a known prostitute and that it was quite possible that Kosminski had been a client, it leaves any kind of statement that he was the killer, or was even present during the event, on very shaky ground.
Anyway, the upshot of all this is that we are probably no closer to knowing who dunnit. Authors and researchers will continue to reel out the name of the real JTR, usually homing in on one or other of the usual suspects. Interestingly, although the same names come up gain and again, someone once said that if you could line up all of the most "respected" Ripperologists, then throw back a curtain to reveal the man(or woman?) himself, they would all look at him (or her) and say "WHO?"
Without any doubt, the unsolved crimes of the person or persons known as Jack the Ripper are fascinating, innumerable theories and books have appeared on the subject and it's an absolute guarantee that just as many are still to come, but that fascination comes from the fact that we don't know his identity. Common sense tells us that, yes of course, the right thing is to find who carried out these horrific crimes and to close the case to the satisfaction of the law and the state............
.......but, a mystery is a mystery...........and people love a mystery!
For an introduction to the whole affair, take a look at Casebook: Jack the Ripper and the Wikipedia entry here.