Property Easement Legal Liability Question

[James Slaughter]

I own a building which houses a commercial business on the first floor and two apartments on the second.  To access the two apartments, there are indoor stairs accessed from the sidewalk. Once at the top of the stairs, my tenants have keys to a deadbolt lock allowing them to access a "common hallway" which lead them to their apartments.  The building beside me, and the building behind me also use these stairs for their tenants.  One to the right (they do not use the common hallway) and one who has an apartment at the end of the "common hallway" where our two buildings join together.  This building is in the middle of a small southern town and was built in 1864.  When we questioned the
"common hallway" (our first real estate purchase) we were told, "this is the south, this is the way it's always been down, it's a "gentleman's agreement" by the attorney doing the closing.  The property owner who owns the building which joins ours does pay a part of the electricity and water his tenant uses and the tiny bit of light and heat in the common hallway.  But the question is:  If someone falls down the stairs and breaks their neck, who is liable?  People from two other apartments use the stairs, but technically the stairs is in our building. Thanks in advance!