Rome (CNN) -- An Italian court says it convicted Amanda Knox and her former boyfriend of murdering her onetime roommate in part because of evidence showing that more than one person killed the British student.
The Florence appeals court released its explanation Tuesday, less than three months after it convicted Knox and Raffaele Sollecito in Meredith Kercher's 2007 death in a retrial.
In the more than 300-page document, the court said that a third person convicted in the murder, Rudy Guede, did not act alone, and cited the nature of the victim's wounds.
Ruling Judge Alessandro Nencini, who presided over the second appeal in the case, said Kercher, 21, and Knox disagreed over the payment of the rent in the house they shared in Perugia and that "there was an argument, then an elevation and progression of aggression."
The Florence court in January said that Knox, who also was convicted of slander, was sentenced in absentia to 28½ years in prison. Sollecito's sentence was 25 years.
They were first convicted of murder in 2009, but the verdicts were overturned on appeal in 2011.
Now that the explanation of the verdict has been released, defense lawyers have 90 days to appeal to Italy's high court.
In the document, Nencini focuses on the perceived errors of the appellate court that set Knox and Sollecito free, accusing it of the "absence of logic rigor" when evaluating evidence.
He wrote that some evidence, including a prison diary Knox wrote in the early days of her incarceration, was used to support her innocence when it was "convenient, but at the same time devalued when she incriminated herself."
The judge also reasoned that Knox's false accusation of her former boss, Patrick Lumumba, whom she accused of the killing the night she was arrested, proved her guilt.
Lumumba spent nearly two weeks in prison without Knox correcting her false accusation. He was released when Guede was arrested after his fingerprints were found in at the murder scene.
Nencini wrote that the accusation against Lumumba was "indispensable in understanding the crime" and that the accusation "cannot be separated from the murder."
Nencini also considered credible forensic testimony that the first appellate court dismissed, including traces of mixed blood and DNA belonging to both Knox and Kercher that were identified in the bathroom that the women shared.
"Guede, Knox and Sollecito left traces of their movements in the blood of the victim that was flowing profusely from her wounds," the judge wrote.
Nencini excluded the idea that Guede climbed into the apartment through a window after breaking it with a rock as the Knox and Sollecito defense teams presented in earlier trials.
He also excluded the idea put forth by Guede's defense that Kercher let him in for a prearranged meeting. Instead, he wrote: "The court accepts the position that only Amanda Knox was in possession of the other key to the apartment" and that she let him in.
Nencini dismissed all theories related to a sex game gone wrong. Prosecutors had argued Kercher was stabbed to death after she rejected attempts by Knox, Sollecito and Guede to involve her in a sex game.
Instead, Nencini wrote that the suspects did not need to "share a motive."
He said a knife with Knox's DNA on the handle found in Sollecito's apartment was the weapon that killed Kercher and that Knox left her DNA on the handle when she "plunged the knife into the left side of Kercher's neck, causing the fatal wound."
In the initial trial, a tiny spot of DNA identified on the blade of that knife was attributed to Kercher, but the sample was too small to double test. Nencini nonetheless considered it the primary weapon.
He reasoned that Sollecito used another knife and took it with him when he left. "The English girl was attacked by Amanda Marie Knox, by Raffaele Sollecito, who was backing up his girlfriend, and by Rudy Hermann Guede," Nencini wrote.
Guede is the only person in jail for the slaying, and many aspects of the crime remain unexplained.
Knox and Sollecito have maintained their innocence, and their 2009 convictions led to questions about the effectiveness of Italy's justice system. The trial revealed widespread doubts over the handling of the investigation and key pieces of evidence.
But in March 2013, Italy's Supreme Court overturned their acquittals and ordered a retrial. That proceeding resulted in the convictionsbeing reinstated.
Knox's conviction has raised questions about her possible extradition to Italy to serve her sentence; she was in the United States and did not attend the retrial.
Knox released the following statement reaffirming her innocence Tuesday: