The appeal hopes of Amanda Knox were boosted when a key prosecution witness gave conflicting evidence relating to the killing of British student Meredith Kercher.
The American dubbed "Foxy Knoxy" is battling to get her conviction for the sexual assault and murder of her housemate Miss Kercher overturned.
In a hearing in Perugia, witness Antonio Curatolo - a self-confessed drug addict now in prison for an unrelated conviction - gave contradictory accounts about whether he saw her near the crime scene in the Italian hilltop town.
In the lengthy trial in 2009, the formerly homeless man placed Knox and her ex-boyfriend Raffaele Sollecito - also convicted of the murder - in a square near the house the young women shared on the night of the killing.
He repeated his claim that he had seen the lovers "talking excitedly" in the square and said he thought it was Halloween night - which would be the night before the November 1, 2007 murder.
But at another point he also said he clearly remembered seeing police at the house the morning after he saw Knox and Sollecito in the square - which would be November 1. In fact police went to the crime scene on November 2, when the University of Leeds student's semi-naked body was found in a pool of blood on her bedroom floor, under a duvet.
"Police and Carabinieri were coming and going, and I also saw the 'extraterrestrials' - that would be the men in white overalls," 54-year-old Curatolo told the court with a smile, referring to forensic experts.
His account contradicts Knox and Sollecito's defence that they were at the latter's house when Miss Kercher, 21, from Coulsdon in Surrey, was killed. But his confusion over the dates was said to have cast doubt on his credibility.
Defence lawyers branded him unreliable, though the prosecution maintained that, despite some lack of precision, the witness was lucid and clear in what he remembered. However he also confessed to a long-lasting drug habit, saying: "I have always done drugs... heroin, which is not a hallucinogen."
Sollecito's lawyer Giulia Bongiorno said the hearing "marked an important step forward for the defence's arguments." And Knox's stepfather Chris Mellas, who has moved to Italy to be close to her, said "it couldn't go any better today".