ROME, Italy (CNN) -- A panel of judges in Italy said an American student held in connection with the killing of Meredith Kercher should stay in police custody because evidence suggested she had "fatal capacity for aggression," Italian media reported Wednesday.
A court ruled last week that Amanda Knox, 20, and her Italian boyfriend, Raffaele Sollecito, 23, must remain in jail after lawyers for the pair appealed for their release.
Massimo Ricciarelli, president of the panel of three judges that gave last Friday's ruling, published the reasons for his decision Wednesday, Luca Maori, a lawyer for Sollecito confirmed to CNN.
In his ruling, Ricciarelli said Knox's detention was justified because evidence showed she has multiple personalities, according to the Italian daily newspaper, Corriere della Sera, which published transcripts of the ruling on its Web site.
Corriere della Sera reported the judge as saying that Knox has a "high, we could say fatal, capacity for aggression."
"(Knox) has a disposition to follow whatever drive she has, even when they can end up in violent and uncontrollable acts," the ruling said, according to the paper.
Ricciarelli added that all the evidence suggested Kercher was killed by someone she knew, the paper reported, and investigations suggested that more than one person carried out the killing and that the villa where the body was found had not been broken into.
Prosecutors had earlier accused Knox and Sollecito of staging a break-in to cover up their part in the killing.
Kercher, an exchange student at Perugia's university, was killed on November 1 in the villa where she lived. Investigators found her the next day, with a stab wound to her neck.
Investigators claim they have clear evidence that ties both Knox and Sollecito to the crime scene.
According to the newspaper, the ruling said the lack of evidence of a break-in "proves that the killer did not have to exercise any type of violence in order to enter the house, having used the keys or having been allowed in by the victim herself."
A report issued more than a week ago by an Italian judge suggested Kercher may have been sexually assaulted at knifepoint before she was killed in her bed.
One other suspect is still being held in connection with the case. Rudy Hermann Guede, 20, was arrested after fleeing to Germany. He is the only suspect to have admitted being in the villa on the night of the killing.
Guede claims that an unidentified assailant attacked the British student, his lawyer told CNN. E-mail to a friend
CNN's Hada Messia in Rome contributed to this report