This is regarding cases where the assessee has expired but a return has to be filed by LH using his DSC. Following process is suggested in above regard :

1. The legal heir (LR) has to get a DSC in his own name.
2. LH is required to make a request by sending a mail to ask@incometaxindia.gov.in  mentioning the name, PAN,Date-of-Birth of deceased as well as that of the LH along with scanned attachment of the death certificate of the deceased.
3. On receipt of above, LH would be enabled to file the return of deceased using LH’s DSC.