Perugia murder hunt widens

Police in Perugia are on the trail of a fourth suspect in the murder of student Meredith Kercher.

The 21-year-old from Coulsdon, Surrey, was found with her throat slashed on 1 November in her flat in Perugia, where she was three months into an Erasmus study programme. Her American flatmate Amanda Knox, Knox's Italian boyfriend Raffaele Sollecito and a Congolese musician and bar owner called Patrick Lumumba are in custody accused of the murder.

But investigators say they are now sure that a fourth person was involved. Unidentified fingerprints on Meredith's blood-soaked pillow and DNA on soiled toilet paper in the lavatory have convinced them that at least one other person was in the room when the student was killed.

The position of Ms Knox and Mr Sollecito worsened last week with the news that DNA of Ms Knox and Meredith had been retrieved from the blade of a long kitchen knife found in Mr Sollecito's home – despite the knife having been carefully washed with bleach. The finding opened a new scenario: if this is the murder weapon, and it came from Mr Sollecito's home – Ms Knox and Meredith's two Italian flatmates have never seen it before – then perhaps it was brought to the the flat with the express intent of killing Meredith. In which case she was not, as previously thought, killed impulsively at the culmination of a reckless sex session, but the victim of premeditated murder. Yesterday, a bag belonging to Ms Knox was taken from her in jail for forensic examination in case it contains traces of the knife.

But the mystery fingerprints and DNA convince the investigators that the full picture still eludes them, setting off the urgent hunt for a fourth suspect. Meredith complained to English friends in Perugia that Ms Knox brought too many men to the flat, and attention is focusing on drug dealers and others on the fringes of the student community.

In particular there is a man Ms Knox brought home whom Meredith's friends called "strange", and dubbed "internet man" because he worked in an internet cafe. In Perugia there are also rumours that one of the regular drug dealers who sold hash to the foreign students – Ms Knox and Mr Sollecito admit to having smoked hash "all afternoon" on the day of the murder – has since disappeared.

Yesterday, friends of Mr Lumumba demanded his release. Mr Lumumba, married with a two-year-old son, has denied setting foot in Meredith's flat and no evidence has been found linking him to the crime.