Updated

A young American woman charged with murder in Italy turned cartwheels and sat on her boyfriend's lap in the police station after the killing of her apartment mate, Italian investigators testified at the trial Friday.

The court in this central city heard testimony from detectives who inspected the apartment where 21-year-old Meredith Kercher, a Briton, was found stabbed to death Nov. 2, 2007.

Kercher's roommate, University of Washington student Amanda Knox, and Knox's Italian former boyfriend, Raffaele Sollecito, are charged with murder and sexual violence. They have pleaded innocent and looked tense and somber when they were escorted into court by police guards.

Domenico Giacinto Profazio, the former head of the Perugia police detective squad, recounted the investigation that led to charges against the two defendants and a third suspect convicted in a separate trial last year. Rudy Hermann Guede of the Ivory Coast was sentenced to 30 years in prison.

Profazio said Knox and Sollecito had a "strange attitude" when they were taken to the police station for questioning following the discovery of Kercher's body. He said that on one occasion Knox sat on Sollecito's lap.

"I told them it was not appropriate," Profazio said.

He also recalled other officers reporting that Knox was doing cartwheels and splits in the station.

Prosecutors allege Kercher 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. They say Guede tried to sexually assault Kercher and then Knox fatally stabbed her in the throat.

Profazio testified that records show Knox's and Sollecito's cell phones were switched off at around 8:30 p.m. on the night of the slaying, making their whereabouts untraceable.

A second witness, police officer Marco Chiacchiera, said no record was found of a telephone call that Sollecito claims to have received on his apartment landline phone at 11 p.m.

Sollecito maintains he was in his own apartment and doesn't remember if Knox spent part or all of the night with him.

Knox initially told investigators she was in the house when Kercher was killed and covered her ears against the victim's screams. Later, she said she wasn't there.

Kercher's family lawyer, Francesco Maresca, called the cell phone detail "highly significant."

"The phones were always on, and were switched off exactly that night, from the evening to the next day," Maresca told reporters.

But Knox's father, who attended the hearing, said it was not unusual for his daughter to switch her phone off.

Curt Knox told reporters his daughter was coping with her detention.

"She is doing OK," he said. "She had her freedom taken away from her for 16 months. How would you feel if your freedom was taken away from you for 16 months?"

Knox also played down his daughter's purported bizarre behavior at the police station.

"It probably is a kid who's never been exposed to something as gruesome as this. Maybe it's her way of dealing with that," he said. "In a conversation with me she would stretch to her toes, you just get used to that."

He exchanged a tight, brief hug with his daughter before she was ushered out of the courtroom at the end of the session.

A third witness, Monica Napoleoni, who heads Perugia police's homicide squad, described the crime scene and Kercher's body, which was found semi-naked in her bedroom, partially covered by a duvet.

"Her eyes were opened. She has been massacred," Napoleoni said, adding that a blood-soaked bra was also found at her feet.

Napoleoni recalled feeling that Sollecito and Knox seemed "indifferent to everything" when they were at the police station for questioning. "They would make faces, kiss each other, while there was the body of a friend in those conditions," she said.

Napoleoni also denied allegations that police hit Knox during an interrogation. "We gave her drinks, chamomile tea, we took her to have breakfast at the cafeteria. Amanda was treated well," she said.

During Friday's testimony, DNA evidence that prosecutors say points to Knox and Sollecito was also listed.

Prosecutors say Knox's DNA was found on the handle of a knife that might have been used in the slaying, and the victim's DNA was found on the blade. The knife was found at Sollecito's house.

They 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.