(Reuters) - Italy's conviction of Amanda Knox for the murder of her British roommate when the two were exchange students together could spur a drawn-out fight over extradition in the United States, where supporters contend she is the victim of a faulty foreign justice system.
If Knox's conviction is ultimately confirmed pending further appeals, her lawyers are expected to argue that the United States cannot send her to Italy in part because of U.S. constitutional guarantees against "double jeopardy," although some experts say that could be a tough case to prove.
Knox and her former Italian boyfriend Raffaele Sollecito were found guilty on Thursday for the second time in the 2007 stabbing death of Meredith Kercher, in a retrial that reversed an earlier appeal judgment that cleared her.
Knox, who spent four years in an Italian jail before returning to the United States in 2011, was sentenced to 28 years and 6 months but will not face jail time pending further appeals in Italy. Knox did not attend the trial and would have to be extradited to serve her sentence.
"She has powerful legal arguments that she can use to fight extradition, or the U.S. can use to deny extradition," said Sean Casey, a New York-based former federal prosecutor. "Under the law, the Constitution trumps a treaty."
Now 26 and a student at the University of Washington, Knox said she would not willingly return to Italy.
"I'm going to fight this until the very end. And it's not right, and it's not fair and I'm going to do everything that I can," she told ABC News' "Good Morning America."
If Italian authorities ultimately seek her return, Knox could find herself in a U.S. federal courtroom to fight it, and experts were split on her chances of prevailing on legal grounds.
Some said a constitutional ban on being retried for the same offense after an acquittal would trump an American-Italian extradition agreement. U.S. courts may also frown on her having been tried in absentia, they added.
Others counter the treaty implies an acceptance of the Italian justice system, and that the legal case for extradition is strong.
"You'd have to show a complete breakdown of their judicial system," said Julian Ku, an international law expert at Hofstra University. "There's no problem of hometown bias for the victim because she was not a local. There's no evidence of corruption."
SUPPORT AT HOME
Initially portrayed as a sex-obsessed party girl, Knox has been commonly seen in her home country as a victim of a judicial process riven with breakdowns in police procedure, mishandling of crime scene evidence and prosecutorial misconduct.
Knox's lawyers argued that only one person is guilty of the murder: Ivory Coast-born Rudy Guede, who is serving a 16-year sentence for sexually assaulting and stabbing Kercher. But his trial found that he did not act alone.
In a measure of the support Knox has received close to home, U.S. Senator Maria Cantwell, a Washington state Democrat, said she was "very concerned and disappointed" by the verdict.
In a move that would be rare but not unprecedented, the U.S. Secretary of State has the final right to veto an extradition request, and legal analysts said Washington might feel political pressure to keep Knox out of an Italian prison.
The U.S. State Department has said officials will continue to monitor the Knox case.
"There's a lot of reasons it wouldn't sit well with folks in our country to see her extradited," said Robert Anello, a New York-based attorney and expert in international criminal law. "That would weigh heavily on the political end."
Washington has proven willing in the past to shield citizens from Italian justice. In 2009, U.S. officials said they would not extradite 23 CIA members convicted in absentia in Italy of kidnapping an Egyptian cleric under the U.S. "extraordinary rendition" program.
A decade earlier, two U.S. Marines whose jet clipped the cable of a ski resort gondola, killing 20 people, were tried in a U.S. military court over the objection of Italian prosecutors. They were found not guilty of involuntary manslaughter.
Denial of extradition would be met with disappointment by Italian officials but would be unlikely to precipitate a diplomatic crisis, several U.S.-based analysts said.
"There are limits to how seriously they feel about actually getting a hold of her," said Paul Rothstein, a law professor at Georgetown University who said an extradition process could take months, if not years, to reach a final conclusion. "They could have acted earlier, more vigorously."
(Additional reporting by Eric Johnson in Seattle; Editing by Cynthia Johnston and Gunna Dickson)