CFSL sources confirmed that the video footage of the hotel's CCTV, where Pushkar was found dead, along with the viscera which was preserved after the post-mortem, have been received by the agency on Friday and tests in the laboratory have begun.
Police have requested the CFSL Director Rajinder Singh to expedite the whole process in the case and sought a report as soon as possible, sources said.
According to the experts, it takes more than 50 hours to test the viscera.
On Tuesday, a sub-divisional magistrate had directed Delhi Police to investigate the murder or suicide angle in the case after autopsy report has cited the death as "sudden and unnatural" while the cause of death was mentioned as poisoning.
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However, the nature of the poison and the quantity can only be established after viscera tests at CFSL.
In a report to the police, SDM, who has recorded the statements of Sunanda's brother, son, Tharoor and his staff, had said that no family member suspected any foul play in the death.
The autopsy report had mentioned more than a dozen injury marks on Sunanda's both hands and an abrasion on her cheek which suggests a "use of blunt force", besides a "deep teeth bite" on the edge of her left palm.
The case, which was initially handled by South District police as the incident took place in Sarojini Nagar area was handed over to the Crime Branch on Thursday. However, the case was transferred back to the South District police on Saturday.