Amanda Knox looks on from the prisoner’s dock in Perugia court.
Police took DNA samples and other evidence from the apartment of the slain British student Meredith Kercher.
After 27 years on remand, Amanda Knox has been freed from prison in Italy.
Her sentence for the murder of her British flatmate was reduced to 26 years by an appeals court in Perugia, which overturned her original conviction.
Knox was returned to her family home in Seattle, where her family are believed to be welcoming her home.
Her conviction for murder and sexual assault in 2009 had sparked a frenzied international debate about free speech and the limits of criminal evidence.
The appeals court judge said DNA evidence did not prove whether the crime took place in the apartment where Kercher was found with her throat slit, or in Knox’s room three doors away.
Ms Kercher, a 21-year-old student from Leeds University, was studying in Perugia in 2007 when she was attacked by Knox and Knox’s Italian former boyfriend Raffaele Sollecito.
The BBC’s Rupert Wingfield-Hayes, in Perugia, says the sentence is an unusual one because it revokes the original verdict.
Ms Knox had hoped to return to the US with her family after years in a high-security prison in Perugia, but there was a potential problem of her imposing criminal record.
She had been convicted by the trial court in 2009 of the murder and sentenced to 26 years in prison.
The first trial judge ruled that the evidence was unreliable and the acquittal was unlawful, and she was sent back to jail after appealing.
Her Italian ex-boyfriend, Raffaele Sollecito, has been given a 24-year sentence, the same as the first trial’s verdict, but appeals over that.
Another man, Rudy Guede, was also convicted in a separate trial and sentenced to 30 years.
Some 15 other people have been convicted but only four face a full hearing for various charges.
Prosecutors told AFP news agency on Friday that they were considering an appeal to Italy’s highest court.
Their initial appeal to Italy’s highest court to quash Knox’s acquittal in the murder case was rejected by a panel of three judges in June last year.
However, an appeals court in Perugia overturned her conviction and reduced her sentence from 26 years to 26 years last week.
In the original trial, prosecutors said that, along with Knox and Sollecito, Rudy Guede was the prime suspect, but there was no DNA evidence connecting him to the crime.
Knox said she was “relieved” at the outcome of the appeal.
Speaking to AFP, she described “a system that was shameful, which was hypocritical, which was unjust”.
“It was only because I am a person of colour, for me it felt like my civil rights were trampled upon,” she said.
“This couldn’t have happened in America – my life would never have been threatened. This is not a fair world.”
Guede, who has always denied the crime, said that he hoped to serve his sentence in a regular prison and escape the spotlight.
Mr Sollecito said he was “sad for Meredith’s family, but I am also pleased for me and Amanda”.
Asked if he was taking this opportunity to escape the international spotlight and media interest, he responded: “Yes, very much so. You know the temptation is always there. This is the biggest show on earth.”
A hearing is set for Tuesday on whether he should remain under house arrest.
BBC Royal commentator Mark Easton said that from a legal point of view, the lower court’s conviction of Knox for the murder and sexual assault of Ms Kercher had never stood up.
“It is the aftermath that will cause the greatest scandal to her family and friends. If she had tried to claim refuge in America, it would be one thing, but to return to her hometown in Seattle, her old schoolmates would resist her return with every fibre of their being,” he said.
“The crime left the family members of Meredith, who were in Perugia to support the victim, with more questions than answers.”
Miss Kercher’s mother Arline told reporters that her family were happy to see Knox returned home and thanked “her supporters around the world”.
She described the decision as a miscarriage of justice and demanded the investigation be reopened.
Prosecutors said that Guede had confessed and was guilty of the murder.
Mr Sollecito’s lawyer asked for him to be jailed immediately for another six years while Mr Guede’s lawyers said they would appeal.
BBC correspondent Murray Mogerson in Perugia says the whole question of an acquittal and the original