A bench of Justices G S Sistani and Chander Shekhar said that the police had collected evidence in the matter in February 2015, but was yet get the final result of the electronic evidence they seized in the case including that of the close friends of Tharoor and Pushkar.
"This (collection of evidence) is something that happened in February 2015. Why has the police not been able to get the final result even after two years," the bench asked.
The court said it has to look into the aspect of a delay.
"We are also concerned as to who is the real culprit," it said.
"Here is somebody who passed away back in 2014 and you (police) initially said it was a case of suicide, but later it turned out to be one of homicide," the bench said.
The court's observations came during hearing of plea by Bharatiya Janata Party leader Subramanian Swamy who has sought a court-monitored CBI-led special investigation probe into Pushkar's death.
Tharoor's stepson Shiv Menon has sought his impleadment as a party in the matter after Swamy moved the court seeking a probe.
Senior advocate Vikas Pahwa, appearing for Menon, has also questioned Swamy's locus in seeking such a probe alleging that he was doing it only for publicity.
Objecting to the locus issue of the petitioner raised by Menon's counsel, Swamy said, "There is no lack when it comes to publicity and I am a national-level politician."
He said he was only trying to stop the police from covering up the investigation in the case.
Swamy alleged that Pushkar's son is not at all interested in knowing the reason behind the death of his mother and is only interested in her property in Canada.
"He (Menon) was in jail in Dubai in connection with a narcotics case. Tharoor got him out," Swamy claimed.
The BJP leader said that he could show a letter which "proved" that Menon was "concerned" about his mother's property.
Advocate Pahwa, however, submitted, "I (Menon) do not think anybody else will be more concerned about my mother's death.
"I have not given any authority to anyone to file any petition on my behalf," his counsel said, adding that a prayer has been made for a direction to the police to conclude the probe and submit the final report in the case.
To this, the bench said, "We do not think that this has been done for a publicity."
It said the petitions filed in matter were aimed at putting pressure on the police as they have not done anything in the last three-and-a-half years.
The bench also asked advocate Divakar, representing the Delhi Police, as to whether he was satisfied with the status report filed in the case.
He replied that the prosecution was "satisfied" with the investigation as of now and was trying to get more information.
The bench, however, was not convinced with the police' submission with regard to the difference of opinion in the findings of the Central Forensic Science Laboratory and the Forensic Science Laboratory, both based in Ne Delhi.
The court also expressed its displeasure over the contention in the status report that data from some of the mobile phones, seized during the investigation, have been deleted and the Indian forensic laboratories have been unable to retrieve the same.
The police, meanwhile, said that approvals for sending these devices to their manufacturers abroad for chip-level retrieval are being obtained from the competent authorities.
The court, however, directed the police to file an additional affidavit with regard to the probe into the matter and listed it for further hearing on August 30.
Swami has moved a fresh application seeking a copy of the charge sheet to be filed by the city police in the matter within 45 days.
He has alleged that the police was misleading and delaying the case as it had withheld from the medical board constituted in the matter, certain crucial evidences from the crime scene.
Earlier, the bench had expressed displeasure over the failure of the police to file a charge sheet in the case.
Pushkar was found dead under mysterious circumstances in a suite of a five-star hotel in south Delhi on the night of January 17, 2014.
Swamy, along with advocate Ishkaran Singh Bhandari in their plea, has alleged that "inordinate delay" has been caused in the investigation "which is a blot on the justice system".
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