Two independent forensic experts testified that investigators made glaring errors in collecting DNA evidence, including using a dirty glove and not wearing caps.
Prosecutors say DNA evidence was found on what was believed to be the murder weapon and on the clasp of the victim's bra.
That evidence played a crucial role in securing the convictions of Knox and her co-defendant Raffaele Sollecito in the 2007 murder of Meredith Kercher, a Briton who shared an apartment with Knox while they were both exchange students in the city of Perugia.
In footage and framegrabs shown to the court, two police officers collected the bra clasp, and the glove worn by one of the two appeared to be dirty on two fingers. Forensic expert Stefano Conti noted the bra clasp was collected 46 days after the Nov. 1, 2007 fatal stabbing of the 21-year-old Kercher.
"Over those 46 days several objects were moved, and at the same time several people will have come in and out," Conti noted, again stressing the risk of contamination.
The other expert, Carla Vecchiotti, said the review concurred with the original testing in saying that the genetic profile on the knife's black plastic handle could be attributed to Knox. The knife was found at her ex-boyfriend Raffaele Sollecito's apartment. Kercher's body was found at the apartment she shared with Knox.
Knox, 24, and Sollecito, 27, have denied wrongdoing and have appealed. The evidence review was granted at the request of their defense teams.
Knox's mother, Edda Mellas, said Monday's hearing marked a good day for her daughter, though she has repeatedly cautioned during the trial that she will only celebrate if Knox walks free when a verdict is reached in late September.
The independent experts will be questioned and cross-examined in the next hearing scheduled for Saturday. That will be the last hearing before the summer break.
The Associated Press contributed to this story.
