Amanda Knox, a 20-year-old American student, has apparently given a partial confession in the grisly stabbing death of her exchange student roommate, Meredith Kercher.

Authorities say Knox admitted hearing Kercher scream the night she was murdered, and gave a partial confession, but kept changing her story.

Kercher, a British citizen, was found dead and half naked in a pool of blood in her home about 100 miles north of Rome, Italy, with a deep slash in her throat. Authorities believe she was fighting off a sexual attack,

Amanda Knox, her boyfriend, and another man are detained in the investigation into the attack.