Knox and Sollecito had pizza dinner with Sollecito's friends. Sollecito was asked to go to the police station after dinner to answer a few questions. They arrived between 10:30 and 11 PM. Knox voluntarily went to the police station.
Knox did her stretches/yoga/cartwheels to capture the officer's attention ... and succeeded. Sollecito was answering questions. At some point, he admitted that he told a load of rubbish and claimed that the rubbish he told was to appease Knox.
Some time after 11, Knox was asked to answer a couple of questions. We know that she couldn't communicate with the officers, as a translator was requested. It took about an hour for the translator to arrive. After questions were asked in Italian, they were translated to English, the questions were answered in English, and then the English answers were translated to Italian ... meaning the conversation took twice as long as it would have taken had everyone spoken the same language. By 1:30 AM, Knox signed an English language, typed statement confirming the testimony she gave to police. That statement changed her status from witness to suspect and she was arrested.