Meredith Kercher's brother has said Amanda Knox should be handed over by the US despite the American saying she is "frightened and saddened" after being found guilty again of murder.
An Italian court yesterday reinstated her conviction for killing the British student.
Knox's ex-boyfriend Raffaele Sollecito was also found guilty after judges ruled the pair should not have been cleared on appeal in 2011.
Knox and Sollecito were charged in 2007 after Miss Kercher's semi-naked body was found with her throat cut in the bedroom of the house she shared with Knox in the central Italian city of Perugia.
Kercher (21) had been sexually assaulted.
Two years after the pair were found guilty at their original trial in 2009 - and handed jail terms totalling more than 50 years - the verdicts were overturned and both walked free from court, with Knox returning to the US and going on to sign a book deal.
Their acquittals in 2011 came after a damning 100-page report outlined a catalogue of errors and breaches of procedure that had been made in collecting evidence.
The third trial began last September in Florence. After nearly 12 hours of deliberations on Thursday, the court upheld the 2009 convictions.
Speaking at a news conference on Friday morning, Lyle Kercher, Meredith's brother, said "If somebody's found guilty and convicted of a murder - if an extradition law exists between those two countries - I don't see why they (the US) wouldn't".
"It would set a difficult precedent if a country such as the US didn't choose to go along with laws they themselves uphold when extraditing convicted criminals from other countries" he added.
Knox (26), who was in her hometown of Seattle when she learned her conviction had been reinstated, has been sentenced to 28 years and six months. She described the decision as "unjust".
"Having been found innocent before, I expected better from the Italian justice system," she said.
Raffaele Sollecito has reportedly been stopped at the Slovenian border
"The evidence and accusatory theory do not justify a verdict of guilt beyond a reasonable doubt. Rather, nothing has changed. There has always been a marked lack of evidence. My family and I have suffered greatly from this wrongful persecution" she added.
Sollecito (29), who was not in court for the verdict but had attended lengthy hearings earlier in the day, was sentenced to 25 years. Reports in Italy say he is now being held by police after being stopped near the country's border with Slovenia on Friday morning.
Lawyers for Knox and Sollecito have said they intend to appeal to Italy's highest court and a long legal battle for Knox's extradition is expected.
Speaking this morning Meredith's sister Stephanie said they are still on a journey to the truth.
