The final, tragic hours of the 21-year-old student's life were disclosed in a 19-page document used at a court hearing in Perugia on Friday.

Judge Claudia Matteini's report suggested that Miss Kercher's throat was slit after she was subjected to prolonged and drug-fuelled sexual assault.

The student's American flatmate, Amanda Knox, Knox's Italian boyfriend Raffaelle Sollecito, and Congolese immigrant Lumumba "Patrick" Diya allegedly wanted to try an "extreme experience".

The judge said: "There are no doubts that there was desire to try a new sensation for the boyfriend and girlfriend, while for Diya there was the desire to have sex with a girl who had turned him down."

The report said Miss Kercher's neck had been cut twice before a third wound which proved fatal. It added that a pocket knife owned by Sollecito was compatible with the wounds and was probably the murder weapon.

A report by pathologist Luca Lialli said Miss Kercher suffered a slow and painful death which would have been hastened if her carotid artery had been severed by the blow.

The judge ruled that the three suspects could be kept in jail for up to a year while the police investigation continues. All three deny any involvement in her death.

Giuliano Mignini, the investigating magistrate leading the murder inquiry, has confirmed police are hunting a fourth person.

The body of the European Studies student, from Coulsdon, south London, is due to be flown back to England this weekend.