Did the tenant request a pre-move out walkthrough? If so, what did the landlord say at that time?
What, if anything, does the lease say about carpet cleaning? When was the last time the carpets were professionally cleaned?
Did the tenant take pictures to document the condition of the apartment at move-out?
A California landlord may charge cleaning fees, but only in the amount necessary to make the apartment as clean as it was when the tenant originally moved in.

