PERUGIA, Italy (AP) âÄî An American student turned somber and buried her face in her hands Thursday when the blood-covered face of the woman she is accused of murdering was shown in video footage at her trial in central Italy. Amanda Knox, 21, quickly looked away and held her head down when images of Meredith Kercher’s body at the murder scene were shown in court. Knox and her former boyfriend Raffaele Sollecito are on trial in Perugia for murder. Both deny any wrongdoing. The American student had been exchanging smiles and whispers with Sollecito, who sat some distance away, but her expression darkened when police official Claudio Cantagalli showed videos detailing the blood-splattered room, Kercher’s face and her foot sticking out from a duvet. Sollecito, 25, kept on looking. The body of British student Kercher was found Nov. 2, 2007, in the apartment she shared with Knox. Prosecutors allege she was killed during what began as a sex game, with Sollecito holding her by the shoulders from behind while Knox touched her with the point of a knife. Prosecutors have alleged that a third man, Ivory Coast national Rudy Hermann Guede, tried to sexually assault Kercher and then Knox fatally stabbed her in the throat. Guede was convicted of the murder in a separate trial last year and sentenced to 30 years in prison. Knox’s father, Curt, who attended the hearing, said the video was “upsetting.” “She already went through the pain of losing her friend, and having to look at it again is not something you want to do,” he told reporters at the end of the proceedings. Earlier this month, behind closed doors, the eight-member jury viewed graphic images from Kercher’s autopsy. Prosecutor Giuliano Mignini said then that Knox kept her head down, while Sollecito glanced at the images occasionally. During other testimony on Thursday, forensic experts described how they documented and photographed bloody footprints, shoe prints and fingerprints found in the apartment. The video footage and other photographs showed Kercher’s bra on the bedroom floor near the body, a bloody hand print on the wall and bloodstains on the clothes closet and door handle. More bloodstains, as well as a footprint, were found in the adjoining bathroom and living room. The experts on Thursday did not specify whether the evidence matched any of the suspects, but a hand print on Kercher’s pillow has been already identified as Guede’s. According to prosecutors, DNA from Knox and Kercher was found on a knife that investigators believe may have been the weapon used in the slaying. The knife was found in Sollecito’s home. Also on Thursday, the head of the forensic unit that intervened in the hours that followed the murder insisted that there was no sign of contamination of evidence collected at the crime scene. Prosecutors say they found Sollecito’s DNA on the clasp of the victim’s bra, although his defense team says the bra bore multiple DNA traces and maintain the evidence might have been inadvertently contaminated during the investigation. Official Alberto Intini, who did not take part in the two inspections that were carried out by the forensics, rejected defense lawyers’ allegations. “In this probe, we did not find any traces of anyone intervening,” Intini testified, as he was shown photos from the murder scene that appeared to show that some objects, such as the doors of Kercher’s clothes closet, were moved between the first inspection on Nov. 2 and the second more than a month later. “DNA doesn’t fly, like pollen or hair, or get thrown upon things here and there,” Intini said. “Even if in theory contamination can never be ruled out, it is not easy for it to happen, and there must be direct contact.” The court lifted the confiscation order on the house where Kercher was killed, returning the apartment to the owners. The judge, jurors, prosecutors and defense attorneys inspected the location last week.