The mother of murdered Coulsdon student Meredith Kercher said she was "surprised and very shocked" by an Italian court's decision to overturn the convictions of Amanda Knox and Raffaele Sollecito.

The decision by the supreme Court of Cassation is the final ruling in the case, ending the long legal battle waged by Ms Knox and her ex-boyfriend.

Ms Kercher, 21, from Coulsdon, was sexually assaulted and stabbed to death in her bedroom in 2007 while studying in Perugia, Italy.

Arline Kercher, Meredith's mother, said she had heard little more about the decision other than the verdict.

She told the Press Association: "(I am) a bit surprised, and very shocked, but that is about it at the moment.

"They have been convicted twice so it's a bit odd that it should change now."

Asked whether she had any plans following the ruling, she said: "I really don't know at the moment, I haven't got any plans."

Ms Knox, who was Ms Kercher's flatmate and a student from Seattle in the US, and Mr Sollecito spent four years in jail for the murder but were acquitted on appeal in 2011.

Ms Knox returned to the US before an appeal court threw out the acquittal and reinstated her and Mr Sollecito's guilty verdicts last year.

But Italy's highest court today overturned last year's convictions and declined to order another trial, Ms Knox said she was "tremendously relieved and grateful" at the decision, saying in a statement that knowing she was innocent gave her "strength in the darkest times of this ordeal".

She added that she had relied on her family and friends and thanked her supporters, while her family expressed "profound gratitude" to those who had helped her.

Following the court's decision, Ms Knox's lawyer Carlo Dalla Vedova said: "Finished! It couldn't be better than this."

Ms Knox, who is now 27, awaited for the verdict in her home town of Seattle. Her Italian former boyfriend Mr Sollecito, 30, had his travel documents seized while the court proceedings were continuing.

The judges will release the reasons for their decision within 90 days after concluding that a conviction could not be supported by the evidence.

The Kercher family's lawyer, Francesco Maresca, said earlier this week: "The interest of the family is to arrive to the end of this trial. They want to be able to remember Meredith outside of the courtroom."

Prosecutors claimed that Ms Kercher, a Leeds University student, was the victim of a drug-fuelled sex game gone wrong.

But Ms Knox and Mr Sollecito consistently protested their innocence and claimed they were not in the apartment the night she died.

Rudy Guede, a drug dealer, is serving a 16-year sentence over the death.

Ms Knox said last year she would become a "fugitive" if convicted and would have to be taken back "kicking and screaming" to Italy.

Last month she announced her engagement to 27-year-old musician and school friend Colin Sutherland, who wrote to her while she was in jail.

Francesco Maresca, the lawyer for the Ms Kercher's family, was disappointed by the ruling.

He said: "I think that it's a defeat for the Italian justice system."