(CNN) -- A grocer has told a court in Italy that an American woman accused of murdering British student Meredith Kercher was in his shop the morning after the death, contradicting the timeline she had previously given.
Both Raffaele Sollecito (left) and Amanda Knox deny charges of murder and sexual assault.
Amanda Knox, 21, has said she was at the home of her former boyfriend and co-accused Raffaele Sollecito, 24, until 10 a.m. on the day after Knox's roommate, Meredith Kercher, was stabbed to death. She said she then left for her house to take a shower.
But on Saturday, witness Marco Quintavalle said a young woman he identified as Knox came into his supermarket near Sollecito's house in Perugia at 7:45 a.m. on November 2.
He said the woman was waiting for him to open up, and that he exchanged glances with her when she entered.
"It really struck me, she had a very pale face and these light eyes," Quintavalle said. "I can still see the image in my head."
Asked by the presiding judge Giancarlo Massei if that woman was in the courtroom, Quintavalle said he was sure it was Knox. "It's her, I'm sure of it," he said, looking at her, according to the Daily Telegraph. Knox did not appear to react.
After the death police found a receipt at Sollecito's house for cleaning products from the shop where Knox was allegedly spotted, the paper said. Officers say bleach and cloths found in the house were used to clean the knife used in the murder and the murder scene itself.
Knox and Sollecito are charged with murder and sexual assault in the November 2007 killing of Kercher, who died in what prosecutors called a "drug-fueled sex game" with the couple and a third person, Rude Guede.
Guede was convicted of murder in October and sentenced to 30 years in prison. He is expected to be one of about 100 witnesses in the case.
Kercher was found dead in her bed, half-naked, with a knife wound to her neck. In court papers, prosecutors state that Sollecito held Kercher by her wrists while Knox poked at her with a knife and Guede sexually assaulted her.
Prosecutors say they have physical evidence placing the defendants at the scene, and that they gave investigators confusing and contradictory statements about their whereabouts the night Kercher died.
Knox first said she was at the house she shared with Kercher, then changed her story, according to court records.
Sollecito, meanwhile, said he was never at the house, but was at his apartment, watching a movie on his computer with Knox. Later, he told investigators he did not remember whether Knox was with him the entire night.
Defense lawyers are expecteed to argue that the physical evidence was tainted by sloppy police work.
The trial, which is expected to take months, has drawn more than 140 journalists from 86 news outlets to the courthouse in Perugia, a university town about 185 km (115 miles) north of Rome.