Italy's Supreme Court overturned Amanda Knox's acquittal on Tuesday, according to the Washington Post.

Knox is the American exchange student who served four years in an Italian prison for the killing British student Meredith Kercher, before being acquitted in late 2011.

"It was painful to receive the news that the Italian Supreme Court decided to send my case back for revision when the prosecution's theory of my involvement in Meredith's murder has been repeatedly revealed to be completely unfounded and unfair," Amanda Knox said through a family spokesman.

"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."

Knox hopes for "an objective investigation and a capable prosecution."

"She thought the nightmare was over," Knox's attorney Carlo Dalla Vedova said after the decision was released.

In 2007, Amanda Knox, then 20, moved to Perugia, Italy, to attend the University For Foreigners of Perugia. She shared a room with another student studying abroad, 21-year-old Meredith Kercher from England.

In November of that year Kercher's semi-naked corpse was found at the Perugia apartment she shared with Knox, who became a prime suspect. Police arrested Knox and her then-boyfriend Raffaele Sollecito.

After serving four years in an Italian prison for the murder, the pair was acquitted in late 2011.

In addition to overturning the acquittal, Italy's Supreme Court also upheld a slander conviction against Amanda Knox.

During her 14-hour interrogation Knox accused a Perugia pub owner of being the killer. The man was held for two weeks based on her accusation, but was released for a lack of evidence.

Knox's former boyfriend Sollecito's attorney, Giulia Bongiorno, points out that the acquittal getting overturned is not a conviction by the courts.

"It's a decision that cancels a verdict and orders a retrial," Bongiorno said. "I'm not concerned about a deeper reading of the documentation, because I know the documentation."