Just working on a bit about this for my book. As with the thing where Phillip Flynn is alleged to have built Croxteth Hall despite the fact that no-one seems to have any clue who he is, I have hit a bit of a brick wall with regards to the ghost said to haunt cell G2 (presumably cell number 2 in G wing) at the prison. Various sources, both online and in print give the name of the man supposed to have inhabited the cell prior to being hung in 1927 (or thereabouts) as William Kennedy. One source suggests that an accomplice called Guy Frederick was also hanged at Walton and that the men killed a police Constable.
However, I can find no record of either man being hung at Walton nor of any such crime at the time. I'm ready to simply chalk this up as another case where there aren't enough facts to really draw a conclusion but I thought I'd post here and see if anyone else has ever heard of either man or has any idea how I might lay my hands on a complete list of everyone ever hanged at Walton. 60 men and 2 women in total apparently by the way.