Rudy Guede has been found guilty of killing Meredith Kercher, while former lovers American Amanda Knox and Italian Raffaele Sollecito will stand trial for the murder.
Ivorian Guede was sentenced to 30 years in prison by a judge in Perugia in Italy.
All three were accused of killing the 21-year-old Leeds University exchange student in a violent sex game in the city last November and have spent nearly a year behind bars awaiting the decisions.
The semi-naked body of Miss Kercher was found in her room in the cottage she shared with Knox and others on her year abroad. She had died of stab wounds after her throat was slit.
Knox, 21, from Seattle - nicknamed Foxy Knoxy - and her former lover Sollecito, 24, are accused of killing Miss Kercher in a bungled sex game with Guede.
The trial is set to begin on December 4.
The key piece of evidence used by prosecutors to link Sollecito to the crime is a trace of his DNA on the clasp of Miss Kercher's bra. His lawyers argued this was due to accidental contamination during the investigation.
They have also said that if Sollecito had removed the victim's bra there would be more traces of his DNA on it and they would not only be on the clasp.
Knox's parents Edda Mellas and Curt Knox were in Perugia while their daughter's fate was decided behind closed doors. Miss Kercher's family were also in the Umbrian hilltop town to hear the judge's decision.
Guede, 21, originally from the Ivory Coast, requested a separate fast-track trial from Knox and Sollecito because he feared they had a pact to frame him for the murder. Guede was the only suspect who admitted being in the house at the time of the murder but, like the other two, denied any wrongdoing.