Hi Darren,
I agree it is mind boggling that descendants from both families are discussing this incident 158 years later.
Unfortunately I don't think I have much more than you already have. My mother has recorded that her grandfather told her that "one of our ancestors was tried for murder after knocking a man down. This man hit his head on the floor and died and our ancestor was acquitted."
It was only after I came across the report in the Lincolnshire Chronicle that I realised who it was. I found the report of the trial in the Stamford Mercury dated March 16th 1855 - which I assume you have?
I have inherited quite a few of William Brumpton's (1810-1886) possessions, including his notebooks filled with his business dealings (cattle etc) but I haven't found any reference to this incident.
Did you manage to find any old photos of the Kings Head? I walked through Caistor yesterday and it is now, sadly, a dress shop & the sign has been removed.
Regards,
William