The court was hearing a plea on the matter by A G Perarivalan, one of the convicts whose death sentence was commuted to life term in the assassination case.
He has alleged that neither the CBI's special investigation team, nor the Multi Disciplinary Monitoring Agency (MDMA) headed by it, had proceeded with the probe in a proper perspective to bring the accused to book, as several top people were involved in it.
The bench asked the CBI to file a detailed investigation report along with a time-frame within which the probe would be completed. It also directed the agency to indicate the legal hurdles, if any, and the steps taken to overcome these issues.
During the hearing, Additional Solicitor General Maninder Singh told the apex court that investigation was going on and it would take some time as some accused were absconding.
More From This Section
He said the matter would require extradition proceedings since some of the absconding accused were out of India.
Responding to the query, Singh said "yes" but it would take some time.
He argued that the CBI has already filed a counter affidavit in the matter and that Perarivalan's conviction has been upheld by the apex court, while the probe into several aspects of the case was going on.
"With or without him (Perarivalan), this matter has to be investigated. What benefits he may get out of the investigation will be seen later," the bench said and fixed the matter for hearing on August 16.
The apex court had earlier sought the response of the Centre and the CBI on the plea which has alleged that CBI did not probe the conspiracy behind the killing of Rajiv Gandhi in 1991 despite an order from a TADA court in Chennai.
The apex court had on Febraury 18, 2014 commuted the death sentence of Perarivalan to life imprisonment, along with two other condemned prisoners -- Santhan and Murugan -- on grounds of a delay of 11 years in deciding their mercy plea by the Centre.
He had also referred to the inquiry report of the Justice Jain Commission that had probed the conspiracy aspect of the assassinaation and which had formed the basis for the TADA court's order for a further probe to identify the role of individuals to uncover the larger conspiracy in the murder.
The convict had alleged that the CBI and the MDMA, which were entrusted with the task to probe the facts, have not done their work properly.
"The grievance of the petitioner is that the designated TADA Court was monitoring the pending investigation on paper only, but without knowing the actual facts of the investigation being conducted by CBI (MDMA) for the last about 17 years.
Rajiv Gandhi was assassinated on the night of May 21, 1991 at Sriperumbudur in Tamil Nadu by a suicide bomber at an election rally.