Updated at 5:00 p.m. EST
An American student accused of fatally stabbing her British roommate in Italy had a growing hatred for the victim and killed her in retaliation during a drug-fueled sex game, a prosecutor contended Friday in closing arguments at her murder trial.
Lead prosecutor Giuliano Mignini argued that Amanda Knox, together with her ex-boyfriend and co-defendant Raffaele Sollecito and a third man convicted in a separate trial last year, killed Meredith Kercher under "the fumes of drugs and possibly alcohol." Knox and Sollecito tried to cover up their crime by staging a burglary, he contended.
Knox, of Seattle, wanted to get back at Kercher for saying she was not clean and for calling her promiscuous, Mignini argued.
"Amanda had the chance to retaliate against a girl who was serious and quiet," Mignini said. "She had harbored hatred for Meredith, and that was the time when it could explode. The time had come to take revenge on that smug girl."
Knox, who has denied wrongdoing, appeared to be weeping as Mignini described the wounds on Kercher's body. Her lawyer, Luciano Ghirga, sitting next to her, at one point held her hand. Looking discouraged and keeping her head down, she was hugged and comforted by lawyers during breaks.
Mignini recalled previous testimony by Kercher's friends, in which the Briton reportedly expressed surprise and irritation at Knox's behavior. Knox has denied having major problems with Kercher and has said in the past she was shocked at the death of a woman she considered a friend.
Knox and Sollecito are charged with murder and sexual violence in the 2007 killing in the central Italian town of Perugia. Sollecito also maintains he is innocent.
As the trial nears its end, Knox's parentsthat their daughter would be found innocent.
"If the decision is made from the evidence in the court of law, she will be found innocent," Curt Knox told CBS' "The Early Show" Friday. Knox described his daughter as "anxious."
Ivory Coast citizen Rudy Hermann Guede is appealing his conviction and 30-year sentence handed down after the fast-track trial he requested.
In his appeal, Guede claims that he saw Knox running from the crime scene - a charge that has been reported publicly and could potentially sway her trial.
"It's a concern because the jurors are not sequestered," Edda Mellas, Knox's mother, told "The Early Show" co-anchor Maggie Rodriguez. "However, what I've been told is that his story just wasn't credible. He says that Amanda arrived at her own house and rang the door bell. That doesn't make any sense. So, you know, yes, it's disturbing, but we're not too worried."
Ultimately the case against Knox and Sollecito rests largely on circumstantial evidence, with little solid proof to show what really happened that night, reports CBS News correspondent Elizabeth Palmer.
Mignini contended that Knox, Sollecito and Guede met at the apartment where Kercher was killed on Nov. 1, 2007, shortly before the slaying, likely to settle some drug issues with Guede, who was known in Perugia for dealing drugs. According to the prosecutor, Kercher and Knox started arguing and then the three brutally attacked the Briton.
Kercher's body, her throat slit, was found in a pool of blood the next day.
Occasionally raising his voice during his seven hour-long argument, Mignini described what he called "an unstoppable crescendo of frenzied violence," which began with Knox and Sollecito trying to take off Kercher's clothes and threatening her.
At one point, Knox hit Kercher's head against a wall, then tried to strangle her, as Sollecito held her and Guede sexually assaulted her, Mignini alleged.
"They realized that Meredith would not give up fighting and at that point, the match had to be brought to an end," he said.
Mignini said Knox used a knife to cut Kercher's throat, causing the deepest wound, while Sollecito used another knife to threaten her.
According to prosecutors, a knife with a 6 1/2-inch (16.5-centimeter) blade with Kercher's DNA on the blade and Knox's on the handle was found at Sollecito's house.
"That is the weapon with which Amanda inflicted the deadly blow," Mignini said. Defense lawyers argue that the knife is too big to match Kercher's wounds and the amount of what prosecutors say is Kercher's DNA is too low to be attributed with certainty.
Prosecutors also maintain Sollecito's DNA was found on the clasp of Kercher's bra, although his defense team contends that the evidence might have been inadvertently contaminated during the investigation.
Also on Friday, Mignini said that Knox and Sollecito staged a burglary in the apartment by breaking a window in a bedroom in an attempt to sidetrack the investigation.
A rock was found in a bedroom, and witnesses testified that shattered glass was found all over clothes on the floor, suggesting the window was broken after the room was put into disarray.
"The key to the mystery is in that room," Mignini said, adding that it would be nearly impossible to climb through the window without getting cut and leaving blood on the shattered glass.
Also, he argued, that window, the most exposed of the apartment, was an unlikely choice for a burglar. Nothing in the room with the broken glass, which belonged to a roommate of Knox and Kercher, was reported missing, Mignini noted.
"All of this was done to channel suspicions on a stranger, and divert them from those who had the apartment keys," he said.
Knox's defense lawyer Carlo Dalla Vedova said Mignini's reconstruction was "suggestive," but it failed to present solid evidence.
Prosecutors were expected to formally make their sentencing requests to the eight-member jury Saturday, while a verdict is expected in early December. They are expected to request life in prison Italy's stiffest punishment.
The 22-year-old Knox maintains she spent the night of the murder at Sollecito's house in Perugia. The 25-year-old Sollecito has said he was home working at his computer that night. He said he does not remember if Knox spent the whole night with him or just part of it.
Defense lawyers for Knox and Sollecito are working on the theory that Guede was the sole attacker.