Amanda Knox's appeal success leaves unanswered question: who was real murderer?

Prosecutors who saw their case collapse over discredited DNA evidence will take an appeal against the new verdicts of innocence for Ms Knox and her co-defendant Raffaele Sollecito to Italy¿s highest court.

Amanda Knox at Leonardo Da Vinci airport in Rome as she prepared to return home to the United States after four years in jail. REUTERS / ANSA / TELENEWS

PERUGIA // Amanda Knox flew home yesterday after four years in an Italian prison, as the dramatic reversal of her murder conviction stunned the victim's family, angered the prosecution and left questions unanswered over who killed her British roommate.

Prosecutors who saw their case collapse over discredited DNA evidence have announced they are taking an appeal against the new verdicts of innocence for Ms Knox and her co-defendant Raffaele Sollecito to Italy's highest court. The family of the victim, 21-year-old Meredith Kercher, said during an emotional news conference that they were back to "square one."

Lyle Kercher, a brother of the victim, said: "If those two are not the guilty parties, then who are the guilty people?" .

A lawyer for the sole man now convicted for the stabbing death of Kercher, Ivory Coast native Rudy Hermann Guede, said yesterday he will seek a retrial. Prosecutors had maintained the three killed Kercher during a lurid, drug-fueled sex game.

Kercher's half-naked body, with more than 40 wounds, was found in 2007 in the apartment she shared with Ms Knox in the Umbrian hill town of Perugia, where both were studying.

The local newspaper La Nazione had its front-page dominated by a huge photo of a crying Ms Knox, overwhelmed by emotions as the verdict was read out Monday night in a packed courtroom in Perugia.

To Ms Knox, the verdict means freedom after four years behind bars and under the spotlight of an international press focused on her every word or gesture. The case has been a cause celebre in the US, and a staple of British tabloids, which took to calling her "Foxy Knoxy."

She was soon on her way home, protected by the darkened windows of a Mercedes that led her out of the Capanne prison in the middle of the night, and then yesterday morning to Rome's Leonardo da Vinci airport, where she boarded a flight to the United States.

"Those who wrote, those who defended me, those who were close, those who prayed for me," Ms Knox wrote in a letter released just hours before leaving the country, "I love you."

But she leaves behind a country shaken by a case that raised questions over its justice system. Moments after the verdict was announced, hundreds of mostly university-age youths gathered in the piazza outside the courtroom and jeered at the news. "Shame! Shame!" and "Murderers!" they yelled.

Prosecutor Giuliano Mignini expressed disbelief at the verdict and said he will appeal to Italy's highest criminal court after receiving the reasoning behind the acquittals, due within 90 days.

"Let's wait and we will see who was right. The first court or the appeal court," Mr Mignini said yesterday. "This trial was done under unacceptable media pressure."

Mr Mignini noted that the jury upheld Ms Knox's conviction on a charge of slander for accusing bar owner Diya "Patrick" Lumumba of carrying out the killing. The judge set the sentence at three years, less than the time Ms Knox had spent in prison.

The highest court's remit is to rule on whether any procedures had been violated, and the hearing generally takes one day in Rome. Defendants are not required to attend.

If the highest court overturns the acquittal, prosecutors would be free to request Ms Knox's extradition to Italy to finish whatever remained of a sentence. It is up to the government to decide whether to make the formal extradition request.

Mr Mignini has been conducting the investigation from the start, and said he never had any doubts that the defendants were guilty. In 2009 he won murder convictions for the two and heavy sentences: 26 years to Ms Knox and 25 to Mr Sollecito. But the prosecution's case was blown apart by a DNA review ordered during the appeals trial that discredited crucial genetic evidence.

Prosecutors maintain that Ms 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 Mr 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 defence, 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.

The review was crucial in the case because no motive has emerged and witness testimony was contradictory. Mr Mignini's description of Mr Knox as a manipulative liar also failed to sway the eight-member jury.

*Associated Press with additional reporting by Reuters