Part of the law about adverse possession in Arkansas has to do with the payment of property taxes. The neighbor hasn’t paid any of the taxes on the property so he can’t claim that as a reason.
Only time will tell. :0(
Sadly for your friend, the neighbor doesn't have to have paid any taxes whatsoever on the property if he's claiming it under adverse possession.
However, tell your friend not to give up so easily! As I mentioned before, you friend may have a good case.
IF your friend can show the court he complained to the neighbor (the sheriff could be compelled to be your friend's witness) --AND that he did it before the neighbor had used the land for the period named by Arkansas law (either 15 or 7 years, depending on the kind of property)-- then the neighbor doesn't have a claim.