Police investigating the murder of Meredith Kercher in Perugia are hunting a man and a woman whom they believe may also have been involved in the killing, it was claimed yesterday.

Italian newspapers reported that blood and “organic substances” on tissues found in Ms Kercher’s bedroom and in the street outside are not from any of the three suspects currently being detained.

The DNA on the tissues belongs to “a male and a female”, reports said, implying that five people were suspected of involvement in killing Ms Kercher, who was found with her throat cut on the morning of November 2.

Amanda Knox, 20, an American student, her boyfriend, Raffaele Sollecito, 23, and Rudy Hermann Guede, an immigrant from Ivory Coast and a petty drug dealer, are all being held over the killing.

New witness 'saw Meredith suspects together'

Amanda Knox, Raffaele Sollecito and Rudy Guede were see at the house in Perugia where the American student died

Multimedia

• Murder in Perugia

BACKGROUND

• Meredith Kercher: Q&A

• New DNA not from Meredith suspects

• Timings crucial to Kercher murder investigation

Related Links

• Dying Meredith Kercher ‘whispered initials of killer’

• Meredith suspects overheard in shop

Sources have suggested that a group of people may have been at the cottage for an evening of sex and drugs.

Mr Guede, who is in custody in Koblenz, has added details to his testimony, telling German police that he had been at the cottage where Ms Kercher was living, after they arranged a date, and had seen her being stabbed by an unknown man. Ms Kercher had managed to whisper the initials “AF” to him, which he took to be those of the murderer and which he claimed he had written on the bedroom wall. Police have revealed no such find.

Police now believe that two knives, not one, may have been used in the assault on Ms Kercher. The initial report by Claudia Matteini, the investigating judge, confirmed a finding by the pathologist in the case that the wounds on Ms Kercher’s throat were compatible with flick knives owned by Mr Sollecito. However, a kitchen knife was subsequently found at Mr Sollecito’s flat bearing traces of Ms Kercher’s DNA at the tip and of Ms Knox’s DNA nearer the handle. One theory is that a flick knife or similar weapon was used to inflict two minor wounds while the kitchen knife was used to cause the much deeper wound from which she slowly bled to death.

It was also revealed that Ms Kercher’s jawbone was fractured, as if her head had been forced back. Further reports said that police who went to the cottage that Ms Kercher shared with Ms Knox and two Italian women found the British student’s clothes in the washing machine. Tests for fingerprints will be done on Ms Kercher’s bloodstained bra — one of the garments not put in the machine by the time that police arrived.

Mr Guede said that he had met Ms Kercher, 21, with some Spanish friends in a pub on Hallowe’en night, and that they had made a date for the next evening. Mr Guede said: “We kissed each other a bit, we touched each other a bit, but I didn’t rape her.”

He went to the lavatory, and because he had earphones on he did not hear the killer enter, though he did hear Ms Kercher scream. He emerged to see “an Italian I didn’t know” stabbing her. The unknown man had said as he fled: “You’re in trouble, you black bastard.” Mr Guede had heard her whisper the initials, and also said that he had tried to save Ms Kercher but it was too late and he too fled in panic. Investigators said his version was “a highly improbable fantasy”.

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