Amanda Knox cries after hearing the verdict overturning her conviction and acquitting Monday in Italy.

PERUGIA, Italy — 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 in the sexual assault and stabbing death of her British roommate.

Knox, 24, collapsed in tears after the verdict was read, her lawyers draping their arms around her in support. 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.”

The eight-member jury acquitted both Knox and Sollecito of murder after a court-ordered review of the DNA evidence cast serious doubts over the main DNA evidence linking the two to the crime.

While the court won’t release its reasons for clearing the two for weeks, the discrediting of the DNA evidence was believed to have been the fatal blow to the prosecution’s case in the absence of a clear motive.

The jury had two options to acquit: determining there wasn’t enough evidence to uphold the conviction or that the pair simply didn’t commit the crime. The jury determined the latter, clearing Knox and Sollecito completely.

Even if prosecutors appeal the acquittal to Italy’s highest court, nothing in Italian law would prevent her from returning home to Seattle. An Italian lawmaker who has championed her case, Rocco Girlanda, said she could fly out as early as today from Rome.

About 90 minutes after the verdict was handed down a black Mercedes carrying Knox was seen leaving the prison.

The jury upheld Knox’s conviction on a charge of slander for accusing bar owner Diya “Patrick” Lumumba of carrying out the killing. But he set the sentence at three years, meaning for time served. Knox has been in prison since Nov. 6, 2007, five days after the murder.

The Kercher family looked on grimly and a bit dazed as the verdict was read out by the judge after 11 hours of deliberations. Outside the courthouse, some of the hundreds of observers shouted, “Shame! Shame!”

“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 victim’s sister, Stephanie Kercher, who was in Perugia with her mother and brother for the verdict, lamented that Meredith “has been nearly forgotten.”