It sounds as though you were the victim of criminal conduct, at the hands of your step dad's mother. It is possible that any of your parents that were aware of this conduct have some criminal liability. I am assuming that the person who gave you the shot was not a medical professional licensed to administer intravenous medicine. Therefore you should also have a civil suit against that person for tortious assault.
Answered on May 21st, 2013 at 11:55 AM