Italy’s Supreme Court’s decision to retry Amanda Knox for the murder of her British roommate Meredith Kercher sparks a heated legal debate that raises questions of double jeopardy.

The U.S. constitution bans double jeopardy, or being tried twice for the same crime; however, the Italian courts have no such law, meaning that they will use the same evidence to try Amanda Knox for the 2007 murder.

According to legal experts, Italy’s Supreme Court decision could throw both countries into uncharted territory, as it is highly unlikely the U.S. will extradite Amanda Knox to face trial.

Amanda Knox’s Italian lawyer, Carlo Dalla Vedova, said it was unlikely that his client does not intend to return to Italy to face trial, which would likely take place this year or next. However, Amanda Knox can be tried in absentia.

“Amanda does not intend to come back for the retrial,” he said.

“Her home is in Seattle and she doesn’t need to be here.”

Carlo Dalla Vedova added that the decision to order a new trial was shocking.

“She thought that the nightmare was over,” he said on the steps of the courthouse.

“But she’s ready to fight.”

When the Italian courts reach a final decision they can also ask for her extradition, the lawyer told Reuters. At that point, the U.S. Department of State would have to weigh in on the request and make its own decision. The state department would then turn to the U.S. Attorney’s Office to seek the Seattle resident’s extradition.

Regardless of the outcome, the new trial will prove to be an expensive and emotionally-charged spectacle.

After the court’s decision, Amanda Knox struck back: “No matter what happens, my family and I will face this continuing legal battle as we always have, confident in the truth and with our heads held high in the face of wrongful accusations and unreasonable adversity,” she said in a statement.

Amanda Knox has largely avoided the public eye since returning to Seattle, Washington, and has been spotted around the town running errands and resuming her studies.

Her memoir, Waiting to be Heard, is due out in April.

Amanda Knox’s memoir, Waiting to be Heard, is due out in April 2013

Meredith Kercher, 21, a Leeds University student, was found semi-naked with her throat cut in the bedroom of the house she shared with Amanda Knox, in Perugia in November 2007.

The first trial caused a stir as both Amanda Knox and her then boyfriend Raffaele Sollicito were acquitted of Meredith Kercher’s murder, and a polarizing divide in national thought. Americans largely understood the two to be innocent, while the British believed them to be getting away with murder.

The initial trial also put Amanda Knox’s character in the forefront as prosecutors painted the American student as a sexual deviant who experimented with marijuana.

But in 2011, the evidence was re-visited and much of it was found to be “contaminated”.

Amanda Knox and Raffaele Sollecito spoke on the phone soon after Italy’s Supreme Court’s decision of retrial.

Raffaele Sollecito’s current girlfriend Annie Achille said: “They will see what can be done.”

Annie Achille added that Raffaele Sollecito, who turned 29 yesterday, is “destroyed” and not talking to anyone.

Meredith Kercher, from Coulsdon, Surrey, was in Italy as an exchange student from Leeds University.

She was found dead in 2007, in the cottage she shared with Amanda Knox in Perugia.

Her throat had been slit and her semi-naked body had been covered with a duvet. After a lengthy trial in Perugia, Amanda Knox and Raffaele Sollecito were convicted of the murder in December 2009 and sentenced to 26 and 25 years respectively.

Two years later, Amanda Knox and Raffaele Sollecito were freed after an appeal court found that the case had been botched and DNA evidence contaminated.

A third suspect, Rudy Guede, whose DNA and bloody footprints were found all over the crime scene, is serving a 16-year prison sentence, reduced from 30 years on appeal.

Meredith Kercher’s family welcomed the Italian court’s judgment. Her sister Stephanie said: “We are never going to be happy about any outcome because we have still lost Meredith but we obviously support the decision and hope to get answers from it.

“There are still so many unanswered questions. All we have ever wanted to do is do what we can for Meredith and to find out the truth of what happened that night.”

Amanda Knox had rejoiced after her conviction was sensationally overturned in 2011.

She fled Italy within hours, returning home to the US, where she quickly embraced life as a free woman.

Amanda Knox now shares a flat with boyfriend James Terrano, a classical guitarist, and is studying at the University of Washington in Seattle, where she can be near her parents and three sisters.

She is preparing for the publication next month of a memoir for which she has been paid a reported $3.8 million.

Raffaele Sollecito remained in Italy and is studying robotic surgery at the University of Verona. He has already released a book about his experience. In it he said that he and Amanda Knox were still in touch – he visited her earlier this year and they speak on Skype regularly.

His lawyer Giulia Bongiorno said: “We are still strong. This is not a sentence in itself: this is just an annulment.”

Amanda Knox’s appeal against her conviction for slander – for having falsely accused her boss Patrick Lumumba of the murder – was rejected. She has already served the three-year prison sentence for that conviction, but was ordered to pay Lumumba €4,000 ($5,100) in costs.

The retrial will be held in Florence, with different judges, to avoid accusations of prejudice against Amanda Knox and Raffaele Sollecito.

[youtube uhgPk0LvtG0]