Although you don't provide any information about how the injury occurred that would allow even the most preliminary evaluation of whether you would have had a case, the answer is "no." You can't sue them anymore.  The statute of limitations on personal injuries is two years.  You would have had to sue within two years of the injury.  You don't specify the date of the accident, but since your mother died in August, 2007, it had to be before that.  So your time to sue ran out sometime before August 27 of this year.