CCTV footage appearing to be Amanda Knox could challenge her alibi that she was with her former boyfriend Raffaele Sollecito on the night Meredith Kercher was murdered six and half years ago.
The CCTV footage shows a woman who looks like Knox walking through a car park near to the house she shared with Kercher in Perugia on the night of the murder.
Knox was re-convicted of her former flat-mate's murder this year along with Sollecito and this footage, shown on Italian TV, has emerged as fresh evidence in the trial.
The black and white video footage obtained by the Italian investigative television programme, Quarto Grado, says the woman wearing jeans and a long coat, has similar clothes worn by Knox in the days following the murder and even compares the walk of the two people.
It also claims Kercher is seen on the film two minutes before, heading back to the house.
Rudy Guede, who was jailed for 16 years for the murder, is spotted by the same video camera earlier that day.
The time-stamp on the CCTV footage is 20:53, 1 November 2007, the night of Kercher's killing, but the programme said it could be out 10 minutes either way.
Kercher was found dead in her apartment on 2 November 2007. She had her throat slashed and had been sexually assaulted.
Author Barbie Latza Nadeau, an expert on the case, told The Times the legal teams were aware of the video but neither side chose to use it in court.
"It's not helpful to the prosecution or the defence. If the prosecution shows someone like Amanda Knox walking away from the crime scene it's not helpful.
"For the defence, if there is a video of her anywhere near the house it's not helpful to them because her alibi is that she was at Raffaele's house," said Nadeau.
Knox and Sollecito were found guilty for the second time in January this year after the High Court in Italy overturned their acquittals for the killing. Knox was sentenced to 28 and a half years and Sollecito 25 years.
Italian prosecutors now say Kercher was killed after an argument with Knox, which was sparked by Guede defecating in the apartment's toilet. Tensions were heightened further when Kercher blamed Knox for taking money from her room.
It is believed Knox and Sollecito were on drugs and the quarrel escalated into murder.
The appellate court in Florence made public a 337-page document explaining the new guilty verdicts issued to Knox and Sollecito in January.
The court noted at least two knives were used to attack Kercher and that there were finger imprints on her body which indicated she had been held down.The judges argue it was Knox who delivered the fatal knife blow to her 21-year-old roommate.
In his conclusion, judge Alessandro Nencini said Kercher had been murdered as a "result of the progression of aggression and a desire to humiliate Meredith".
He added that "Amanda and Meredith had no reciprocal sympathies towards each other" and that "the presence of all three at the crime scene was proved by their traces in the blood of the victim".
A retrial has been ordered to be held in Florence but Knox has refused to return to Italy to attend any more court hearings.
"I did not kill my friend," Knox told CNN recently. "I did not wield a knife. I had no reason to."