The Ripper murders were a Victorian Watergate. Check out "Jack the Ripper: The Final Solution" by Stephen Knight. (Scroll down to the reviews.) . Interesting speculation that the Ripper was actually a team of three (one of which was Sickert) eliminating some prostitutes who were trying to blackmail British royalty over a bastard child (who was also a target) fathered by the Duke of Clarence. Heavy Masonic overtones, with Sir William Gull as the Ripper, a coachman named Netley, and Sickert doing lookouts and other go-fer duties. (Sickert supposedly had Ripperesque overtones in his paintings and their titles.)
As you mentioned, Cornwell did the DNA thing, along with noticing the similarity of writing paper used in some notes.
Knight makes an interesting observation on the spelling of one Ripper note, mentioning that "knif" for knife was a clue that an educated person was trying to impersonate someone unlettered. He said someone ignorant would have spelled it "nife".
Lots of interesting speculation that ties things together and leads me to believe he found out the truth.
No motive
to blackmail British royalty over a bastard child (who was also a target) fathered by the Duke of Clarence.
Exactly 9 months before Elizabeth Crook, the alleged Royal Bastard, was born, Prince albert Edward Victor was in the middle of a two month tour of Geramay. Also there ware indicarions that he was not so much attracted to the ladies, if you know what I mean.