The family of Amanda Knox has asked lawyers to begin their appeal of the American's murder conviction in Italy after reviewing the court's motivation for the verdict.

The judges who convicted Knox and co-defendant Raffaele Sollecito in December issued the reasons behind the ruling this week.

They found no planning or animosity toward the victim, British student Meredith Kercher. They saw the killing as a result of accidental circumstances in what had started as a sexual assault by another man, Rudy Hermann Guede, an Ivorian also convicted for the 2007 murder.

Knox's family said in a statement Thursday night that "there is a lot of conjecture in these motivations," and that "there is a substantial basis for the appeal."

Knox was sentenced to 26 years, Sollecito to 25.

SLIDESHOW: Italian 'Sex Games' Murder Case