Knox 'did cartwheels' after being told of death

Everyone was distraught except US student and boyfriend, says police chief

After the body of murdered Meredith Kercher was discovered in her bedroom in Perugia, central Italy, her friends and flatmates were all shocked and distraught – with the exception of Amanda Knox and her boyfriend Raffaele Sollecito, a court heard yesterday.

Chief Inspector Monica Napoleoni told the court where the pair are on trial for murder how, at the police station as they waited to be first questioned, Mr Sollecito and Ms Knox "appeared completely indifferent to everything, lying down, kissing, pulling faces and writing each other notes. They were talking to each in low voices the whole time – it was impossible that they were behaving like this when there was a dead body in their house. It seemed strange to everybody". Ms Knox had also "turned cartwheels and done the splits," she said.

But, hours later, Ms Knox's behaviour changed abruptly. On the evening of 2 November 2007, the day the murder was discovered, Ch Insp Napoleoni and police colleagues took Ms Knox and Mr Sollecito back to the house where the Ms Kercher had died, in Via della Pergola in the centre of Perugia, where she and Ms Knox had been living. They wanted to check the knives in the kitchen.

Ms Knox collapsed when they got there. "She [Ms Knox] confirmed that no knives were missing," she told the court. "The first time I saw her collapse was at the entrance to the house," she said.

Ms Knox has claimed that she was treated badly during her long interrogation, and that a policewoman had repeatedly beaten her on the head.

Ch Insp Napoleoni denied flatly that such treatment had been meted out. "She was treated very well," she said. "There was absolutely no violence, she was given things to drink, camomile tea, croissants to eat."

She said she was struck by the contradictions in the accounts given by Ms Knox and Mr Sollecito as to how and where they had passed the evening and night on which the murder occurred. "There were so many contradictions in their evidence that it didn't seem real at all," she said.

Earlier yesterday, there were rowdy exchanges in court as other senior Perugia police officers who headed the investigation fought off persistent defence insinuations that the crime scene had been contaminated by careless police work.

Chief Superintendent Giacinto Profazio, the head of the investigation, said that the crime scene had been subject to investigations between 2 and 6 November, and afterwards was sealed. About six weeks later, he said the forensic police returned to the now-sealed flat and found the clasp of the bra belonging to Ms Kercher with Mr Sollecito's DNA on it – a key element in the prosecution's evidence.

Ch Insp Napoleoni conceded that the clasp could have been moved inside the flat during the intervening weeks. Prosecutors allege that Ms Kercher was killed during what began as a sex game, with Mr Sollecito holding her shoulders from behind while Ms Knox touched her with the point of a knife. They say a third man, Rudy Guede, who was convicted last year, tried to sexually assault Ms Kercher before fatally stabbing her in the throat. All three deny murdering Ms Kercher. The trial continues today.