ROME (AP) -- Amanda Knox, who maintained that she and her former Italian boyfriend were innocent in her British roommate's murder through multiple trials and nearly four years in jail, was vindicated Friday when Italy's highest court threw out their convictions once and for all.

"Finished!'' Knox's lawyer Carlo Dalla Vedova exulted after the decision was read out late Friday. "It couldn't be better than this."

The surprise decision definitively ends the 7{-year legal battle waged by Knox, 27, and co-defendant Raffaele Sollecito, 31, to clear their names in the gruesome 2007 murder and sexual assault of British student Meredith Kercher.

The supreme Court of Cassation panel deliberated for 10 hours before declaring that the two did not commit the crime, a stronger exoneration than merely finding insufficient evidence to convict.  Instead, had the court-of-resort upheld the pair's convictions, Knox would have faced 28  years in an Italian prison, assuming she would have been extradited, while Sollecito had faced 25 years.

The case attracted strong media attention due to the brutality of the murder and the quick allegations that the young American student and her new Italian lover had joined a third man in stabbing to death 21-year-old Kercher in a sex game gone awry.

Flip-flop guilty-then innocent-then guilty verdicts cast a shadow on the Italian justice system and polarized trial watchers on both sides of the Atlantic, largely along national lines.

In a statement issued from her home in Seattle, Knox said she was "relieved and grateful" for the decision.

"The knowledge of my innocence has given me strength in the darkest times of this ordeal,'' she said, thanking her supporters for believing in her.

Though it cleared Knox of murder, the supreme Court of Cassation upheld a slander conviction against her for wrongly accusing a Congolese-born bar owner in the murder. The court reduced the sentence to three years. Since Knox already spent nearly four years in Italian prison, she won't have to serve that time. The decision to overturn the convictions without ordering a new trial amounted to a rebuke of another high court ruling two years ago that vacated Knox and Sollecito's 2011 acquittal, ordering yet another trial.  Such a direct contrast in decisions by two high court panels is as rare as the double rainbow that arched over the monumental courthouse near the Tiber river during the deliberations.

The five-judge panel's reasoning will be released within 90 days.

Across the Atlantic, a shout of joy erupted from inside the Seattle home of Knox's mother as the verdict was announced. Several relatives and supporters filtered into the back yard, where they hugged and cheered.

Dalla Vedova said he called Knox to tell her the news, but said she couldn't speak through her tears.

"She was crying because she was so happy,'' he said.

Knox has sought to resume a normal life since returning to the United States three years ago, recently announcing her engagement and writing theater reviews and human interest stories for a weekly paper in her hometown.

Kercher, 21, was found dead Nov. 2, 2007, in the apartment that she shared with Knox and two Italian lawyers-in-training. She was half-nude beneath a duvet soaked in blood with her throat slashed.  Investigators determined she had been sexually assaulted.

DNA evidence in Kercher's room led police to arrest a man from Ivory Coast, Hermann Guede, who was convicted of the murder in a separate trial and is serving a 16-year sentence.

The court that convicted Guede ruled he did not act alone, citing the absence of defensive wounds on the victim and concluding that bruises on Kercher's arms indicating she was restrained while one or two others inflicted numerous stab wounds.

The Kercher family attorney, Francesco Maresca, was clearly disappointed by the decision.

"I think that it's a defeat for the Italian justice system,'' he said.  "Whoever was Guede's accomplice does not have a name.''

Kercher's mother, Arline Kercher, told Britain's Press Association news agency that she was "a bit surprised and very shocked."

"They have been convicted twice so it is a bit odd that it should change now,'' she said.

Also disappointed by the decision was the bar owner, Diya `'Patrick'' Lumumba, who was jailed for two weeks after Knox falsely accused him of the murder and is convinced of Knox's guilt.

It is a strange justice for me, long, uncertain, a little opaque, a lot of darkness,'' he said outside the courtroom. `'This is a judicial error in Amanda's case."

The couple maintained their innocence, insisting that they had spent the evening together at Sollecito's place watching a movie, smoking marijuana and making love.

Knox and Sollecito were convicted by a Perugia court in 2009, then acquitted and freed in 2011, and then convicted again in 2014 in Florence after the Cassation court overturned the acquittals and ordered a new appeals trial.

That Florence appeals conviction was overturned Friday.

In closing arguments, Dalla Vedova pounded away at the absence of any physical trace of Knox in the room where Kercher was found and highlighted doubts about the presumed murder weapon, a bread knife found in Sollecito's kitchen drawer that bore Knox's DNA -- which the defense said was from kitchen use .

The defense lawyer also said Knox's false accusation was coerced by police and obtained without being advised she was a suspect. He has challenged the slander conviction with the European Human Rights Court in Strausbourg.

Sollecito's defense lawyer, Giulia Bongiorno, argued there were errors of `'colossal proportions,'' in the guilty verdicts. 

Sollecito, who turned 31 on Thursday, sat in the front row during hours of arguments during the Cassation Court over two days, a new girlfriend by his side. He returned to his home in southern Italy to await the decision followed by Italian police presumably ready to act in case his conviction had been upheld.

"You have your whole life ahead of you now, Raf," Sollecito's lawyer, Luca Maori, told the Sollecito by cell phone from the steps of the courthouse under the glare of TV cameras.  Sollecito has completed his computer science degree, but has said the notoriety surrounding the case has made it difficult to find a job.

Speaking to reporters, Maori added: "He almost couldn't speak. Eight years of nightmare over."