Walton Gaol - 1891 - Court Records? Prison register?

[lolaclare]

Hi
My GG Grandfather was in Walton Gaol in the 1891 census. His name was William Fleming, he was a sailor/mariner and he was born 1855/6/7 in Ireland.
As far as I can tell he wasn't in for long because he was in the Electoral Register at his home address for 1889-90 and had a child born in Apr-May-Jun 1892.
I've searched the newspaper reports from the Liverpool Assizes and Police Courts and can't find any mention of him. There is also no sign of him in the Criminal Register on Ancestry. How else can I find out what he was in for?
Are there any records from the prison itself in existence for that period? Liverpool Record office say they don't have any, but they could be somewhere else?