She lied and tried to frame an innocent man for the crime. That’s not indicative of innocence. Then there is her DNA on the knife.
The knife they got from the silverware drawer of her boyfriend's apartment.
Time:"The prosecution, she says, is most likely relying on a knife found at the house of Knox's then boyfriend and fellow accused Rafaelle Sollecito. That knife has Knox's DNA on the handle and what some forensic scientists say is Kercher's DNA on the tip. But Bremner dismisses the idea that it is the knife that killed Kercher: "They never found the murder weapon." Bremner claims that a bloody print on the bed linens conveys the shape of the actual murder weapon and that the knife in question "doesn't match an outline of the knife on the bed." Additionally, Bremner says, expert testimony has already indicated that at least two of the wounds on Kercher's neck couldn't have been made by that particular blade. That aside, she points out, it's not surprising that Knox's DNA would be on its handle; she prepared dinner with Sollecito in his apartment.
As to whether the DNA on the tip belongs to Kercher, experts disagree. Patrizia Stefanoni, a police forensics expert who testified in the pretrial hearing in May, suggested that it was Kercher's DNA on the tip of the knife — and that the way the genetic material was positioned indicated the knife had probably been used to puncture the skin. But other experts who have analyzed the DNA evidence for the defense suggest that poor sample quality and possible contamination undermine the accuracy of these results."