Delhi, Sept 26: Delhi Police has written to Canada's Department of Justice seeking details of the deleted chats from the mobile phones of Sunanda Pushkar and her husband, Congress leader Shashi Tharoor.
The police has sent a Letters Rogatory to the department asking them to get details of chat messages from Research in Motion Ltd, a senior police officer said.
Here is a chronology of the case.
January 17, 2014: Sunanda Pushkar found dead at Delhi's Leela Palaces hotel,a day after she was involved in a spat with Pakistani journalist Mehr Tarar on Twitter over the latter's alleged affair with Shashi Tharoor, Congress MP from Thiruvanathapuram.
January 19, 2014: AIIMS Post-mortem reports indicate a case of sudden and unnatural death.
January 21, 2014: The subdivisional magistrate (SDM) says that Sunanda died due to 'poisoning'.
January 23, 2014: The probe into the mysterious death of Sunanda Pushkar transferred to the Crime Branch of Delhi Police.
January 25, 2014: Murder case is transferred back to the Delhi Police.
Read more: In Pics: Sunanda Pushkar death case
September, 2014: Delhi Police gets viscera report from AIIMS doctor.
January 1, 2015: Police registers murder case in connection with the death of Sunanda.
January 21, 2015: Delhi Police's SIT conducts polygraph test on 6 close aides including Tharoors' domestic help Narayan Singh, driver Bajrangi and Sanjay Dewan, a close friend of the couple.
February 2015: Delhi Police sends Sunanda Pushkar's viscera samples and other evidence gathered from the hotel room to an FBI laboratory in US.
June, 2015: Controversy over her death deepened when AIIMS doctor Sudhir Gupta claimed that he was pressured to give a false report in the case.
November 2015: Delhi Police receives viscera report from the Federal Bureau of Investigation (FBI) which confirmed the presence of lidocaine (used to relieve itching, burning and pain due to skin inflammation) in her body.
January 10, 2016: The final report by AIIMS medical board said that Sunanda died of poisoning caused by anxiety drug Alprax. All India Institute of Medical Sciences experts also said there could be chances of an injectable poison, in view of certain marks on Sunanda's body.
January 15, 2016: BS Bassi who was Delhi Police commissioner that time said Sunanda's death was not natural.
February, 2016: A Special Investigation Team (SIT) of Delhi Police questioned Shashi Tharoor in connection with his wife's murder case. Tharoor retierated that Sunanda died due to medication.
July 18, 2016: Delhi Police questions Pakistani journalist Mehr Tarar in connection with the Sunanda's murder case.