As the police is giving its final touches to the chargesheet in the sensational TISS gangrape case, the victim - a 23-year-old US national - has returned to her home town in US.

"The victim returned to her home town in US on June 15 and it is uncertain if she plans to return to India," informed Dr Neela Dabir, chairperson of International Students Office of the Tata Institute of Social Sciences (TISS).

The victim's absence can weaken the prosecution's case, legal experts opine. "The victim's testimony before the trial court will be the strongest to prove the case against the accused especially in rape cases," said special public prosecutor Vijay Pradhan.

In the absence of the victim, the prosecution will have to solely rely on evidence gathered from the crime scene and other medical and forensic evidence.

In the past, similar cases have fallen apart due to the absence of the victim, said advocate and women rights activist Flavia Agnes.

The six arrested accused in the case - Vinamra Soni (23), Harshavardhan Yadav (22), Jaskaran Singh (21), Dev Colabawala (21), Anish Borkatki (21) and Kundanraj Borgonain (22) are all booked under section 376 (g) of the Indian Penal Code (IPC) for gangrape.

Two of the accused - Borkatki and Borgonain have claimed that they had no role to play in the offence and were mere spectators to the crime.

According to the police, on April 11, the victim had gone partying with the accused. The group had eaten and consumed alcohol at a night club in suburban Deonar, where the victim was allegedly forced to drink beyond her capacity, after which she was taken to a flat in Andheri and raped by the six accused.