They constructed a description of the guy from eyewtinesses and feel pretty confident he was the guy. Most everyone is going with the idea it was Chapman.
From the Casebook site:
"Was this the face of Jack the Ripper?
"There's been a flurry of press recently surrounding this portrait, said to be the 'face of Jack the Ripper'. The composite sketch was put together by an analyst at the London Metropolitan Police, to be unveiled as part of a Channel Five documentary in the UK called 'Jack the Ripper: The First Serial Killer'. The drawing is based on a number of contemporary witness descriptions as given to the police, newspapers and inquests at the time.
"How accurate is it? Its impossible to say, but
in all likelihood, the sketch contains more artistic fancy than actual police science. While it is true that we do know of
many witnesses who claimed to have seen Jack the Ripper, we simply don't know which - if any - did actually see the killer. Even then, the descriptions given at the time were very generalized. Modern police sketches, called facial composites, require an in-depth interview with a witness, asking detailed questions about eyes, nose, lips, cheeks, chin, hairline, etc. Most contemporary witness descriptions only went so far as to describe the suspect's height, clothing, and possibly hair and skin color, as well as a perceived 'ethnicity' (many, not surprisingly, claimed he was a 'foreigner' - which at that time and place was generally taken to mean, a Jew).
There simply isn't enough information in the surviving witness testimony to make such a detailed facial sketch of 'Jack the Ripper.'"All that being said, it is interesting to note that this facial composite bears a striking resemblance to Ripper suspect George Chapman (aka Severin Klosowski), who is currently voted as the #1 likely suspect in an ongoing Casebook.org poll."
You're just being contrarian now.
Actually, my wife has always had a fascination with the Ripper, so I keep up on it. It is far from "[m]ost everyone is going with the idea it was Chapman." As a matter of fact, if you go to the poll at the Casebook site, you'll see that while Chapman leads, the top 5 are in a statistical dead heat. And the next 5 are pulling nearly identical numbers, too. So, it's a near 10-way tie for who "[m]ost everyone is going with."