FLORENCE, Italy

- More than two years after Amanda Knox returned to the U.S. apparently home free, an Italian court yesterday reinstated her murder conviction in the stabbing of her roommate and increased her sentence to 28 1/2 years in prison, raising the specter of a long, drawn-out extradition fight.

Knox, 26, received word of the verdict in Seattle, her hometown. The former American exchange student called it unjust and said she was "frightened and saddened."

"This has gotten out of hand," Knox said in a statement. "Having been found innocent before, I expected better from the Italian justice system."

Lawyers for Knox and her ex-boyfriend Raffaele Sollecito, 29, who was also found guilty, vowed to appeal to Italy's highest court, a process that will take at least another year and drag out a seesaw legal battle that has fascinated court-watchers on both sides of the Atlantic.

After nearly 12 hours of deliberations yesterday, the appeals court in Florence reinstated the guilty verdicts first handed down against Knox and Sollecito in 2009 for the slaying of British exchange student Meredith Kercher.

Those verdicts were overturned in a second trial that ended in an acquittal in 2011, and Knox was released from prison after four years behind bars, returning to the United States. But Italy's highest court ordered a third trial.

The Florence court increased Knox's sentence from the original 26 years and handed Sollecito 25 years.

Kercher, 21, was found dead Nov. 2, 2007, in a pool of blood in the bedroom of the apartment she and Knox shared in the central Italian city of Perugia, where both were studying. Her throat had been slit and she had been sexually assaulted.

Knox and Sollecito denied any involvement in the killing, insisting they were at Sollecito's apartment that night, smoking marijuana, watching a movie and making love.

Prosecutors originally argued that Kercher was killed in a drug-fueled sex game gone awry - an accusation that gave the case a lurid cast that fascinated the European tabloids and led to headlines about "Foxy Knoxy" and her sex life.

But at the third trial, prosecutors argued instead that the violence stemmed from arguments between roommates Knox and Kercher about cleanliness and was triggered by a toilet left unflushed by the third defendant in the case, Rudy Guede.

Guede, who is from the Ivory Coast, was convicted in a separate trial and is serving a 16-year sentence for the murder.

Legal experts have said it is unlikely that Italy will request Knox's extradition before the verdict is final.

If the conviction is upheld, a lengthy extradition process will probably ensue, with the U.S. State Department ultimately deciding whether to turn Knox back over to Italian authorities to serve her sentence. Her lawyers are likely to argue that she is the victim of double jeopardy, because she was retried after an acquittal.