Father of student leader Anis Khan who fell from an upper floor of his residence leading to his death in police presence on Tuesday prayed before the Calcutta High Court that the investigation into his son's death be handed over to an impartial agency other than the state police.

Hearing in the petition filed by Salem Khan, the father of Anis Khan, was concluded before a bench of Justice Rajasekhar Mantha on Tuesday as the state claimed that the allegations were against lower rank police personnel and civic volunteer and there was no allegation of conspiracy.

Justice Mantha reserves his judgment in the petition seeking transfer of investigation in the case to an impartial agency for unearthing the truth behind Anis Khan's death.

Concluding his argument in the matter, Khan's lawyer Bikash Bhattacharya submitted that a report by a Special Investigation Team of the West Bengal police does not disclose how and on whose permission the raid took place at the home of Anis Khan at Amta in Howrah district.

The state government had earlier told the court that the post-mortem examination report indicates that Khan's death was accidental and not homicidal as alleged by his father.

Two post-mortem examinations were done on the dead body of Khan, the second being on an order of the court.

The state had submitted that there was no motive for murder as the accused persons - a home guard and a civic volunteer - did not know Anis Khan, and that he fell through an open window of the second floor of his home at Amta in Howrah district on February 19.

The two, who had allegedly gone to the second floor looking for Khan, were arrested by a special investigation team formed by the state government and charged under Section 304A (causing death by negligence) of the IPC.

The state government had on April 19 submitted an 82-page report to the high court, as had been directed by it earlier, indicating steps taken in its investigation into the unnatural death of Khan.

Alleging that his son was murdered by men wearing khaki and civic volunteer uniform, Salem Khan had moved the high court seeking an order for an investigation into the death by an impartial agency which is not connected with the West Bengal police.

Bhattacharya had claimed before the court that Anis Khan had been brutally assaulted by four persons, of whom one was in police uniform and the other three in civic volunteer dress, and thrown off the third floor of his home on the night of February 19.

Khan's family members have been demanding a CBI investigation into his death.