Italy's highest court of appeal has said it is "evident and indisputable" that Rudy Hermann Guede, one of the three suspects being held in connection with the murder six months ago of Meredith Kercher in Perugia, took part in the killing.

At the beginning of this month the Court of Cassation rejected appeals by Mr Guede, Amanda Knox and Raffaele Sollecito to be released from prison, ruling that they must remain in custody. The panel of judges, explaining today its reasoning in the case of Mr Guede, an Ivory Coast immigrant with joint Italian nationality, said there was no doubt he had played a part in the murder, though his precise role was not yet clear.

The judges said that by his own admission Mr Guede - who denies any involvement in the murder - had been at the hillside cottage where Ms Kercher lived as a student "before, during and after the murder". He had also admitted having "incomplete sexual relations" with Ms Kercher, though it had not been possible to establish from forensic evidence whether the sex was consensual or not, the judges said.

The judges said it was also not clear "at this stage" whether Mr Guede, a basketball player and small-time drugs dealer who has lived in Perugia since the age of eight, had carried out the killing, either alone or with others, or had only instigated it. He had none the less taken part "consciously and voluntarily" in the assault on Ms Kercher.

The ruling said Mr Guede's contention that the murder had been committed by "an Italian I did not know" while he was in the bathroom with stomach pains after eating a spicy kebab was "indisputably false" and amounted to the further offence of "furnishing a false alibi".

A week ago the judges explained their reasons for refusing the appeals by Ms Knox and Mr Sollecito, saying that Ms Knox, an American from Seattle who shared the cottage with Ms Kercher and two female Italian students, had a "negative personality". Mr Sollecito, her former Italian boyfriend, a computer science student from Bari in southern Italy, had a "fragile character", which could not be explained away by "innocuous youthful stereotypes" in "a context marked by habitual drug use".

The judges ruled that, if released, the suspects might try to flee or to interfere with evidence. Ms Kercher, a Leeds University exchange student, was found dead in her bedroom on November 2 last year. She was semi-naked under a duvet with her throat cut. Of the three suspects only Mr Guede admits that he was at the cottage on the evening of the murder.

He recently identified Mr Sollecito and Ms Knox as the people he says he saw at the cottage, claiming that he struggled with Mr Sollecito, who was carrying a knife. Mr Sollecito and Ms Knox deny this and claim they spent the evening and night of the crime at Mr Sollecito's flat, smoking cannabis.

In what appears to be an orchestrated media campaign defence lawyers have suggested that forensic procedures were not followed properly and that evidence collected from fingerprints, footprints and a fragment of Ms Kercher's bra strap had been contaminated to the point where it would not stand up in court if charges were brought. The suspects can be held for up to a year before the case is brought to trial.

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