In a major breakthrough, the investigators have recovered an audio clip of Aaftab Amin Poonawalla and Shraddha Walker arguing, sources said on Monday.
Meanwhile, Aaftab has been taken to the Central Bureau of Investigation (CBI) forensic office in Lodhi colony to collect voice sample.
The forensic experts will then match the voice sample with the newly procured audio clip to make fresh breakthroughs in the case.
According to the sources, in the audio clip, the duo can be heard fighting and Aaftab can be heard abusing.
Further details are awaited.
On Friday, Saket court had extended the judicial custody of Poonawala, accused of murdering his live-in partner Shraddha Walkar, by another 14 days.
The court also approved Delhi Police's request to obtain his voice sample in connection with the probe.
On December 22, the Delhi Police filed a request at the court seeking permission to record Poonawala's voice since he is accused of killing Shraddha Walkar.
Shraddha and Aaftab met through the dating app 'Bumble' in 2018. They came to Delhi on May 8 before shifting to Chattarpur area on May 15.
Aaftab allegedly killed Shraddha on May 18, chopped her body into 35 pieces and dumped them at various places over a period of 18 days.