MILAN (AP) -- The Florence appeals court that reinstated the conviction against Amanda Knox in her roommate's 2007 murder said in a lengthy reasoning made public Tuesday that Knox herself delivered the fatal blow, and that the overwhelming physical evidence precluded any need to determine a clear motive.
Presiding Judge Alessandro Nencini concluded in the 337-page document that the evidence "inevitably leads to the upholding of the criminal responsibility" against Knox and her former Italian boyfriend Raffaele Sollecito for the murder of 21-year-old Meredith Kercher in a hillside villa occupied by students in Perugia, a university town.
The judge said the nature of Kercher's wounds inflicted by two knives and the absence of defensive wounds indicated multiple aggressors were to blame, also including Rudy Hermann Guede, an Ivorian man convicted separately and serving a 16-year sentence.
Nencini presided over the panel that reinstated the guilty verdicts against Knox and Sollecito in January, handing Knox a 28 ½ year sentence including the additional conviction on a slander charge for wrongly accusing a Congolese bar owner. Sollecito faces 25 years.
The release of the court's reasoning opens the verdict to an appeal back to the supreme Court of Cassation. If it confirms the convictions, a long extradition fight for Knox is expected. She has been in the United States since 2011, when her earlier conviction was overturned. Knox has vowed to fight the reinstated conviction and said she would "never go willingly" to Italy to face her judicial fate.
Sollecito's lawyer, Giulia Bongiorno, tore apart the reasoning, saying "from the motive, to weapon, to the DNA, it is a string of errors."
"I can't wait until they fix a day to hear us for the appeal, because honestly the verdict is so full of errors, illogical elements and contradictions, that I strongly believe it will be overturned," Bongiorno said.
The judge said relations between Knox and Kercher were strained, despite Knox's attempts to downplay tensions during the trial, and that the two had argued over housekeeping and visitors. He also cited as credible Guede's statements that the British student had accused Knox that evening of stealing rent money from her room, even though none of the defendants was convicted of the theft.
According to Nencini, on the night of the murder, Knox and Sollecito arrived at the house sometime after Kercher, and Knox let Guede inside -- dismissing defense arguments that Guede had broken in.
"It is a matter of fact that at a certain point in the evening events escalated; the English girl was attacked by Amanda Marie Knox, by Raffaele Sollecito, who was backing up his girlfriend, and by Rudy Hermann Guede, and constrained within her own room," the document said.
Nencini's reasoning assigned the role of each assailant: Sollecito, now 30, used a small knife that caused a wound to the right side of Kercher's neck and also was used to remove her bra, the judge wrote, while Guede restrained and sexually assaulted the victim. Knox "delivered the only mortal blow," striking Kercher with a kitchen knife causing an 8-centimeter-deep wound, the judge wrote.
The three trials have only physically identified one murder weapon, a kitchen knife found in Sollecito's drawer. Forensic tests attributed DNA on the handle to Knox and on the blade to Kercher, although that evidence was placed in doubt by new experts in the first appeal that acquitted the pair. No smaller, second knife has ever been entered into the evidence.
The court said it was not necessary for all of the assailants to have the same motive, and that the murder was not attributable to a sex game gone awry, as it was out of Kercher's character to have ever consented to such activity.
"It is not always the case that the motive of a serious, bloody crime is easy to read," the judge wrote, especially when not in the context of other criminal activity such as financial gain. Courts have determined that motives are less relevant when the evidence is clear, he said.
Kercher was found dead in a pool of blood in the apartment she and Knox shared in the town of Perugia, on Nov. 2, 2007. Her throat had been slashed and she had been sexually assaulted. Knox and Sollecito were arrested four days later and served four years in prison before an appeals court acquitted them in 2011. Knox returned to the Seattle, where she is a student at the University of Washington.
Italy's high court later threw out that acquittal in a scathing decision and ordered a new trial, resulting in January's conviction. Both Knox and Sollecito deny any involvement in Kercher's death, and say they spent the evening at Sollecito's place getting high, having sex and watching a movie.
The courts have cast wildly different versions of events. Knox and Sollecito were convicted of murder and sexual assault in the first trial based on DNA evidence, confused alibis and Knox's false accusation against a Congolese bar owner, for which she was also convicted of slander.
Then an appeals court in Perugia dismantled the murder verdicts, criticizing the "building blocks" of the conviction, including DNA evidence deemed unreliable by new experts, and lack of motive.
That acquittal was vacated in March 2013 by Italy's highest court, which ordered a new appeals trial to examine evidence and hear testimony it said had been improperly omitted by the Perugia appeals court, and to redress what it identified as lapses in logic.
Guede, was convicted in a separate trial of sexually assaulting and stabbing Kercher. His 16-year sentence -- reduced on appeal from 30 years -- was upheld in 2010 by Italy's highest court, which said he had not acted alone. Guede, a drug dealer who fled Italy after the killing and was extradited from Germany, acknowledges that he was in Kercher's room the night she died but denies killing her.
Paolo Santalucia in Rome contributed to this report.