How to get refund of last 4-5 years in case of death of assessee

Dear friends, one of my known received a compliance notice for non filing of return. notice is sent in his mother's name his mother is died few days ago when 26AS is checked it is found that tds is drducted by bank on payment of interest on SB A/C u/s 194jA from 2009 to 2015 now he wants to get refund of that tds plz help...