PERUGIA (Italy) - AMERICAN student Amanda Knox weathered a second day of tough questioning on Saturday over charges that she took part in the murder of her British housemate who refused to join in a group sex session in Italy.

Prominent public prosecutor Giuliano Mignini grilled the 21-year-old exchange student over her alleged role in an orgy that turned violent with the stabbing death of Meredith Kercher, 22, of Britain.

Mr Mignini focused on Knox's assertions that aggressive police questioning had led her to make false statements - notably, that her part-time employer Patrick Lumumba was the killer.

The defendant described 'a steady crescendo' of accusations and suggestions that finally led her 'to believe I had forgotten things.' She testified with confidence in fluent Italian, although she addressed all her questioners with the familiar form for 'you,' occasionally prompting murmurs in the courtroom.

Knox had said on Friday that she was also under duress when she stated that she was at home at the time of the murder and could hear Ms Kercher's screams.

Instead, Knox said, she spent the night of November 1, 2007, with her Italian boyfriend Raffaele Sollecito at his flat, where they smoked marijuana, had sex and watched a movie.

Both have been held since a few days after Ms Kercher was found semi-nude in a pool of blood with her throat cut in the house in the walled medieval town of Perugia that she shared with Knox.

Defence lawyer Carlo Dalla Vedova praised Knox's testimony, telling AFP: 'We know that Amanda can explain and sell herself better than anybody else.' He added: 'If you keep a young girl of 20 all night without a lawyer and take advantage of her naivety (you can) get her to tell the story about Patrick.' The Congolese Lumumba, who was held for two weeks before being released without charge, is suing Knox for defamation and was present at the hearing.

Noted lawyer Giulia Bongiorno, who is defending Sollecito, also praised Knox as having been 'very authentic in her responses.' A third defendant in the case, 20-year-old Rudy Guede, from Ivory Coast, has already been convicted and sentenced to 30 years for his role in the murder. -- AFP