The letter to CBI, which is conducting a probe in the multi- crore scam, has been written by Sarbari Mukherjee, mother of Debjani Mukherjee, one of the key accused in the scam. Debjani Mukherjee has been in judicial custody for the last nine years. She has been identified as the closest aide of Saradha Group founder chairman, Sudipta Sen.In t