Lyle Kercher, brother of slain British student Meredith Kercher, and his sister, Stephanie, talk to the media today in Perugia, Italy. Lyle said the family feels it is back to “square one” following the appeals court verdict overturning the conviction of American student Amanda Knox and her former boyfriend.

PERUGIA, Italy — Amanda Knox headed home to the United States a free woman today, the morning after an Italian appeals court dramatically overturned the American student’s conviction of sexually assaulting and brutally slaying her British roommate.

The Italy-US Foundation, which has championed Knox’s cause, said she departed shortly after noon from Rome’s Leonardo da Vinci airport on the way to London, from where she will catch a flight to the United States.

The 24-year-old Knox, who is returning to Seattle, arrived at the airport in a Mercedes with darkened windows and waited for boarding in a private area, out of public view.

Back in Perugia, the family of slain British student Meredith Kercher remained stunned by the verdict and searching for answers.

“It was a bit of a shock,” said Stephanie Kercher, the victim’s older sister. “It’s very upsetting ... We still have no answers.”

Lyle Kercher, a brother, said the family is still trying to understand how a decision that “was so certain two years ago has been so dramatically overturned.”

Lyle Kercher said the family has been left to wonder who is guilty in the 21-year-old Kercher’s death after the release of Knox and her one time boyfriend Raffaele Sollecito on appeal. A third man has been convicted in the brutal slaying, however his trial concluded he did not act alone.

“If the two released yesterday were not the guilty parties, we are obviously left to wonder who is the other guilty person or people. We are left back at square one,” Lyle Kercher said.

Prosecutor Giuliano Mignini expressed disbelief in the verdict, and vowed an appeal to Italy’s highest criminal court.

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

Knox and her ex-boyfriend Raffaele Sollecito were convicted in 2009 of sexually assaulting and murdering Kercher, a 21-year-old British student who shared an apartment with Knox in Perugia. Knox was convicted to 26 years, Sollecito to 25. Both had been in prison since Nov. 6, 2007, four days after Kercher’s body had been found at the apartment.

But, the prosecution’s case was blown apart by a court-ordered DNA review that discredited crucial genetic evidence.

The 24-year-old Knox dissolved into tears as the verdict was read in the packed courtroom.