PERUGIA, Italy (AP) -- Amanda Knox left prison Monday, a free woman for the first time in four years, after an Italian appeals court threw out the young American's murder conviction for the brutal stabbing death of her British roommate after a drug-fueled sexual assault.
Knox, 24, collapsed in tears after the verdict was read, a stunning reversal in a sensational saga that became a cause celebre in the U.S. Her co-defendant and former boyfriend, Italian Raffaele Sollecito, also was cleared of killing 21-year-old Meredith Kercher in 2007.
"We're thankful that Amanda's nightmare is over," her younger sister, Deanna Knox, told reporters outside the courthouse. "She suffered for four years for a crime she did not commit."
About 90 minutes after the verdict was handed down, a black Mercedes carrying Knox was seen leaving the prison. She was expected to board a commercial flight for home on Tuesday.
The fatal blow to the prosecution's case was a court-ordered DNA review that discredited crucial genetic evidence used to convict Knox and Sollecito in 2009. They were sentenced to 26 and 25 years, respectively.
While waves of relief swept through the defendants' benches in the courtroom, members of the Kercher family, who flew in for the verdict, appeared dazed and perplexed. Meredith's older sister, Stephanie, shed a tear, and her mother, Arline, looked straight ahead.
"We respect the decision of the judges but we do not understand how the decision of the first trial could be so radically overturned," the Kerchers said in a statement. "We still trust the Italian justice system and hope that the truth will eventually emerge."
The Kerchers had pressed for the court to uphold the guilty verdicts, and resisted theories that a third man convicted in the case, Rudy Hermann Guede, had acted alone. Guede, convicted in a separate trial, is serving a 16-year sentence.
There were two options to acquit: that there wasn't enough evidence to uphold the conviction or that the pair simply didn't commit the crime. The eight-member jury determined the latter, clearing Knox and Sollecito completely.
The verdict reverberated through the streets of this medieval hilltop town, where both Knox and Kercher had arrived with so much anticipation for overseas studies programs four years ago.
Hundreds of mostly university-age youths gathered in the piazza outside the courtroom jeered as news of the acquittals spread. "Shame! Shame!" they yelled, adding that a black man had been made to shoulder all of the guilt for the murder.
Knox was pale, clearly terrified and appeared breathless as she arrived for the verdict shortly after 9:30 p.m.
Presiding Judge Claudio Pratillo Hellmann read out the verdict in a frescoed subterranean courtroom packed with reporters. In five minutes, Knox's fate was reversed.
"The appeals Court of Perugia ... orders the immediate release of Amanda Knox and Raffaele Sollecito," Hellmann said.
The jury upheld Knox's conviction on a charge of slander for accusing bar owner Diya "Patrick" Lumumba of carrying out the killing. But it set the sentence at three years, amounting to time served. Knox has been in prison since Nov. 6, 2007, five days after the murder.
After the verdict, Knox dropped her head in sobs and had to be propped up by lawyers on both sides of her.
Prosecutors said they would appeal to the nation's highest criminal court, the Court of Cassation, after reading the court's reasoning, due out within 90 days.
"Tonight's sentence is wrong and confounding," prosecutor Giuliano Mignini told the ANSA news agency. "There is a heavy conviction for slander. Why did she accuse him? We don't know."
"The Court of Cassation will establish who is right" between the lower court and the appeals court, he added. Mignini said there was "unprecedented media pressure," revisiting a theme he touched on during his closing arguments.
In the meantime, nothing in Italian law prevents Knox from returning home to Seattle.
At a news conference earlier in the day, the Kerchers expressed hope that the jury would deliberate without considering the intense media coverage of the case.
Stephanie Kercher lamented that her sister "has been nearly forgotten" as attention shifted to Knox and her appeal. "We want to keep her memory alive," the sister said before the verdict.
The trial captivated audiences worldwide. Knox and Sollecito, who had just begun dating, were convicted of murdering Kercher in what the lower court said had begun as a drug-fueled sexual assault.
Lawyers for Knox and Sollecito charged that Guede was the sole killer, but the prosecution and a lawyer for the Kercher family said bruises and a lack of defensive wounds on Kercher's body prove there was more than one aggressor holding her down.
After the verdict, the U.S. State Department said it appreciated the "careful consideration" the Italian justice system gave to the case. "Our embassy in Rome will continue to provide appropriate consular assistance to Ms. Knox and her family," spokeswoman Victoria Nuland said.
In Seattle, about a dozen supporters began hugging each other at a downtown hotel suite.
"She's free!" and "We did it!" they shouted after they watched the court proceedings on TV.
Supporters also expressed sympathy for the Kercher family.
"This is primarily a sad occasion," said Tom Wright, one of the main organizers of the Friends of Amanda group, after the verdict. "They lost their daughter. We'll keep them in our prayers."
Kellanne Henry, a friend of Knox's mother, Edda Mellas, visited the family in Italy.
"It's the first night in four years that (Edda) is going to know her daughter is safe," said Henry, holding crumpled tissues in her hand. "That was a really overwhelming thought for me."
Earlier Monday, Knox tearfully told the court in fluent Italian that she did not kill the woman who shared an apartment with her when they were both students in Perugia. Knox frequently paused for breath as she spoke to the eight members of the jury in a packed courtroom, but managed to maintain her composure during the 10-minute address.
"I've lost a friend in the worst, most brutal, most inexplicable way possible," she said. "I'm paying with my life for things that I didn't do."
Knox said she always wanted justice for Kercher. "She had her bedroom next to mine. She was killed in our own apartment. If I had been there that night, I would be dead," Knox said. "But I was not there."
"I did not kill. I did not rape. I did not steal. I wasn't there," she said.
In his own speech to the jury, Sollecito said: "I never hurt anyone, never in my life."
The prosecution's case was set back during the appeal when two court-ordered independent experts reviewed the DNA evidence that had been used to link Knox and Sollecito to the crime during the first trial.
From the start, the weak point in the prosecution's case was the lack of motive along with unreliable and at times contradictory eyewitness testimony. Therefore, much depended on the scientific evidence gathered by investigators.
Prosecutors maintain that Knox's DNA was found on the handle of a kitchen knife believed to be the murder weapon, and that Kercher's DNA was found on the blade. They said Sollecito's DNA was on the clasp of Kercher's bra as part of a mix of evidence that also included the victim's genetic profile.
But the independent review -- ordered at the request of the defense, which had always disputed those findings -- reached a different conclusion.
The two experts found that police conducting the investigation had made glaring errors in evidence-collecting and that below-standard testing and possible contamination raised doubts over the attribution of DNA traces, both on the blade and on the bra clasp, which was collected from the crime scene 46 days after the murder.
Prosecutors spent several hearings and a significant portion of their closing arguments trying to refute the review, attacking the experts as unqualified, standing by their original conclusions and defending the work of forensic police.
They also pointed to what a prosecutor, Manuela Comodi, called "gigantic, rock-solid circumstantial evidence" that contributed to the original convictions.