ROME – Italy's highest court has overturned the murder conviction of Seattle resident Amanda Knox and her Italian ex-boyfriend, bringing to a definitive end the high-profile case.

The decision by the supreme Court of Cassation is the final ruling in the case, ending the long legal battle waged by Knox and co-defendant Raffaele Sollecito. Both Knox, who was awaiting the verdict in her hometown of Seattle, and Sollecito have long maintained their innocence.

Knox said she was "tremendously relieved and grateful" after the ruling, in a statement. Her family thanked everyone who had supported them and believed in her innocence.

The six judges announced their decision about 10:30 p.m. in Rome (2:30 p.m. PT). They began deliberating at noon after closing arguments by lawyers for Raffaele Sollecito, Knox's boyfriend when 21-year-old Meredith Kercher was stabbed to death.

The ruling, which struck down last year's guilty verdicts by a Florence appeals court, brings the eight-year case to a close. The judges concluded that the evidence did not support a conviction. Their reasoning will be released within 90 days.

The 27-year-old Knox did not return to Italy from her Seattle home for the final appeal. Knox, who had consistently maintained her innocence, was "very worried" in the days before the ruling, said her Italian lawyer, Carlo Dalla Vedova.

While Knox is watching what is happening from Seattle, Sollecito is in Italy. His lawyer made a last-ditch appeal to overturn the pair's convictions for the 2007 slaying Meredith Kercher, Knox's British roommate.

Attorney Giulia Bongiorno began her defense of Sollecito by offering what she called a "little sampling" of the errors and contradictions of "colossal proportions" in the 2014 Florence appeals court verdict that convicted her client and Knox.

Bongiorno noted, for example, that trial documents indicate that there were "no traces of Sollecito in the room" where Kercher, 21, was sexually assaulted and fatally stabbed.

In 2009, Knox and Sollecito were convicted of Kercher's murder, and sentenced to 28.5 and 25 years, respectively. Both served four years before their acquittal by an appeals court in 2011.

Italy's highest court threw out the acquittals in March 2013 and sent the case to a Florence appeals court, which convicted them again in 2014.

Another man, Rudy Guede, was convicted of murder in 2008 and is serving 16 years in an Italian prison. Guede's DNA was found on Kercher's body.