The US will have little legal argument for turning down an extradition request should Italy seek the return of Amanda Knox for the 2007 murder of her British housemate.

A court in Florence on Thursday sentenced Knox to 28 years and six months in prison for killing Meredith Kercher in the university town of Perugia.

Knox was following the proceedings from her home town of Seattle in the US, where she has lived since an acquittal in 2011, which Italian prosecutors appealed.

Her lawyers plan to appeal this latest conviction in turn to the Italian Supreme Court, but if they fail Knox could find herself flying back to a country where she has spent four years in jail.

“As popular as she is here and as pretty as she is here – because that’s what this is all about, if she was not an attractive woman we wouldn’t have the group love-in – she will be extradited if it’s upheld,” Harvard law professor Alan Dershowitz said.

While Knox is seen in the US as the innocent victim of a miscarriage of justice, Dershowitz said there were no legal grounds for preventing extradition.

Nor would it play well diplomatically, given the US demands more extraditions than any other nation, he said.

“The Italian legal system, though I don’t love it, is a legitimate legal system and we have a treaty with Italy so I don’t see how we would resist,” he said.

“We’re trying to get Snowden back – how does it look if we want Snowden back and we won’t return someone for murder?” he asked, referring to fugitive intelligence contractor Edward Snowden.

Knox’s supporters argue the Italian system violates the US legal prohibition on double jeopardy: trying someone twice for the same crime.

Legal experts attach little weight to this argument.

“They always forget she was convicted first,” said Julian Ku, who teaches transnational law at Hofstra University.

Knox and her former Italian boyfriend Raffaele Sollecito served four years in prison for the murder before being released after an appeal led to their 2011 acquittal.

The Italian Supreme Court overturned that ruling in 2013, sending the case back for retrial.

Knox has the right to challenge her extradition in a US court.

A US State Department official confirmed there was an extradition treaty between the US and Italy, but declined to comment on Thursday’s verdict and trial.