My Daughter wants to communicate with her estranged father after 14 years?

My oldest daughter Alex's father and I split up when she was 6 months old. She all of a sudden wants to see him because one of his crazy relatives calls us up and says he is back in town after so long. Should I prevent her from seeing him? or should I do my reasearch and see if he is free of all drugs before I allow her to see him? Or should I let her by all means? I am not sure at all and I told her I would think about it.....Any suggestion would be appreciated!