Rome, March 26 - Reaction was quick, sharp and very emotional to Tuesday's decision by Italy's top appeals court that overturned the acquittal of Amanda Knox and Raffaele Sollecito for the 2007 murder of Meredith Kercher and ordered a new appeal trial. A sister of Kercher, the British student who was murdered while studying in the central Italian city of Perugia, wept with joy at the ruling which she hopes will lead to some justice. But for Knox, Sollecito and their families, the decision by Italy's Court of Cassation was a devastating blow. And the local media in Knox's hometown of Seattle has called the latest appeal process "a real nightmare". Knox, 25, who has been painted in the American media as an innocent abroad, said the news of a retrial was "painful" but she was certain she would again be acquitted. "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," Knox said in a statement issued via a family spokesman. In contrast, Stephanie Kercher wept tears of joy at the decision, saying she hoped the retrial will get to the bottom of what happened to her sister. "I am happy and I want to understand," Stephanie Kercher is said to have told the lawyer representing the family, Francesco Maresca. A Leeds University exchange student, Kercher was found with her throat cut on November 2, 2007 in the house she shared with fellow student Knox. In 2009 Knox and Sollecito, her boyfriend at the time of Kercher's slaying, were sentenced to 26 and 25 years in prison respectively. Those sentences were struck down on appeal in 2011 and Tuesday's decision by the Cassation Court overturns the appeal decision and orders a new appeal trial, which will be held in Florence. Knox, now a student at the University of Washington, could face a demand for extradition if her conviction is reinstated. Rudy Guede, now 26, a native of the African nation of Ivory Coast, is in prison after being convicted separately from Knox and Sollecito and sentenced to 16 years in jail for the murder. The Kercher family lawyer said the victim's family just wants to get the real story. "This decision will help to get to the final, definitive truth about Meredith's murder," said Maresca. "There were other people with Guede. The judges will say who they are. This is a trial victory and a moral victory". In the city of Perugia Tuesday, local residents weren't saying much about the trial. But those who would discuss the case seemed as divided as the courts over what really happened. "At this point Raffaele and Amanda really risk condemnation," said a man in a bar, while a woman argued that the case against the young couple was never proved. And Tuesday's ruling by the top court is not yet the final word in the case, said one of the lawyers representing Sollecito, who turned 29 on Tuesday. "This trial has been an uphill battle from the start and we are climbing one step at a time," said high-profile Italian lawyer and former MP Giulia Bongiorno. "However the decision by the Cassation does not represent a conviction," added Bongiorno. "We will not start again from scratch. Only when we read the motivation for the sentence will it be possible to understand the grounds for the new appeals trial".