For what It's worth, i think this guy
http://wiki.casebook.org/index.php/George_Hutchinson is highly suspicious in the Jack The Ripper case.
A witness puts him at the scene.
He comes forward 3 days later, admits he is the guy seen, and then says he saw the deceased with a man, probably her killer
He gives a very detailed account of what the guy looked like (and names him as a Jew)
Here is where it gets interesting to me:
He says he saw them on the way back from a city and in front of a bar/"hotel". However the bar was not on his way home. So that means he lied about something.
He says the man was 5'5 (about average height at the time). How did he know this? Mary Kelly, the deceased, was 5'7, very tall for a woman at that time. He curiously did not mention she was taller then the man.
In modern police work, we all know that some murderers attempt to insert themselves into a case (Atlanta Child Murders, for example), at the time this was unknown to police.
His home is centrally located to all the crimes. Modern analysis tells us serial killers strike within a comfort zone. His residence is in the middle of that zone.
Very little is known of him, & the Ripper case will never be fully solved, but he is interesting.