PERUGIA, Italy (CBS/AP) Amanda Knox, the American student who denies murdering her British roommate, testified that she was shocked by the death of a woman she considered her friend, and said a "crescendo" of police pressure led her to accuse an innocent man.
Knox, 21, from Seattle, had already told the court on Friday that she was not in the apartment she shared with Meredith Kercher on the night in 2007 when the British woman was slain.
Knox and Italian co-defendant Raffaele Sollecito, her ex-boyfriend, are accused of murder and sexual violence in the slaying of Kercher, who was found in a pool of blood Nov. 2, 2007 in her apartment in the central Italian town of Perugia.
Knox took the stand for the first time Friday and said she spent the night of the killing at Sollecito's apartment. Prosecutors believe Knox, Sollecito and a third suspect convicted in a separate trial went to Kercher's home the night of the murder and killed the British woman in what began as a sex game.
On Friday, Knox repeated accusations that she was beaten by police and confused when she was questioned in the days after the killing. Police have denied any misconduct.
She said it was the pressure that led her to accuse Diya "Patrick" Lumumba, a Congolese man who owns a pub in Perugia, of the killing. Lumumba was jailed briefly but was later cleared and is seeking defamation damages from Knox.
Police have denied any improper behavior, but Knox repeated her claim Saturday when questioned by lead prosecutor Giuliano Mignini.
"It was always a crescendo," she said recalling her early questioning sessions. "When I said I was with Raffaele all the time they told me I was a liar. I was scared, I thought: maybe they are right."
Knox said that interrogators "wanted a name" and that a policewoman hit her twice on the head.
"Do you remember? Do you remember? And then boom! On the head," Knox said, mimicking the slap in court. "I went: mamma mia! And then again, another boom!"
She said it was that pressure that made her come up with Lumumba's name and her initial story that she was at home during the murder and covered her ears against the victim's screams.
"It didn't hurt, but it frightened me," she said of the slaps.
When asked if she had suffered after Kercher's death, Knox said: "Yes. I was very shocked, I couldn't imagine something like that."
She said she considered Kercher "a friend." This contrasted with previous testimony by other witnesses that Kercher had complained about Knox's bathroom habits and had expressed surprise at her apparent promiscuity.
Knox said she felt sorrow over her roommate's death.
"I am very sorry for what happened, sometimes it seems to me it cannot be real," she said.
Knox answered questions confidently and in a steady voice for about five hours, sitting at the witness stand with a prison guard behind her. Though she had an interpreter next to her, the American spoke in fluent Italian, which she mostly learned in the year and a half she has spent in jail.
Prosecutor Mignini said he was satisfied with how Knox's testimony went, adding that he did not consider her credible.
Kercher family lawyer Francesco Maresca said the American was well prepared. "She answered quite satisfactorily, but didn't bring anything new," he said.
Later Saturday, Andrew Seliber, a friend of Knox and a fellow student at the University of Washington, also took the stand, called by the American's lawyers.
In Perugia, "she was having the happiest time of her life," Seliber said. "She worked three jobs responsibly so she had the money to come here."
Knox appeared moved when Seliber walked into the small, frescoed courtroom and she listened carefully to his testimony.
More of Knox's family members and friends are scheduled to take the stand in upcoming sessions. Her mother, Edda Mellas, will testify at the next hearing, Friday.
Knox and Sollecito have been jailed since shortly after the slaying. Sollecito, 25, has said he was at his own apartment the entire night of Nov. 1. He said he does not remember if Knox spent the whole night with him or just part of it. The two have said they could not remember events clearly because they had taken drugs.
Prosecutors allege Kercher came home after an evening with friends on Nov. 1, and soon after opened the door to Knox, Sollecito and Rudy Hermann Guede, who was convicted of murder last year and sentenced to 30 years in prison. Guede, who denies wrongdoing, was given a fast-track trial at his request.
According to the prosecutors, Sollecito held Kercher by the shoulders from behind while Knox touched her with the point of a knife. They say Guede, an Ivory Coast national, tried to sexually assault Kercher and then Knox fatally stabbed her in the throat.
Prosecutors maintain a kitchen knife found at Sollecito's apartment is compatible with Kercher's wounds, and has the Briton's DNA on the blade and Knox's on the handle.
The trial began in January and a verdict is expected after a summer break. Knox and Sollecito could face Italy's stiffest punishment, life imprisonment, if convicted of murder.