PERUGIA, Italy (AP) — An American student accused of killing her British flatmate took the witness stand for the first time Friday, telling the Italian court that she occasionally used drugs at the time of the 2007 slaying.

“Every once in a while, with friends,” Amanda Knox said, speaking English, in reply to a question from a lawyer. She said it was marijuana.

Knox and co-defendant Raffaele Sollecito have told police they had taken drugs the night that British student Meredith Kercher was killed. They said they could not remember events clearly because of that.

Knox smiled as she walked into the court in Perugia, central Italy, before her testimony. Dressed in a white shirt and white trousers, she had her hair pulled in a ponytail. She was called as a witness for civil plaintiffs and her own defense.

Prosecutors contend that Knox, an exchange student from Seattle, and Sollecito, her boyfriend at the time, murdered the 21-year-old Kercher during what began as a sex game. They deny wrongdoing.

Kercher was found Nov. 2, 2007, in a pool of blood in the apartment she shared with Knox.

Ivory Coast national Rudy Hermann Guede was found guilty of murder and sexual violence and was sentenced to 30 years in prison in a separate procedure.