Your money needs an ally. Now more from amanda knox, the american college student, convicted then acquitted of murder in italy. And tonight, facing the possibility of still another trial. She's... See More
Your money needs an ally. Now more from amanda knox, the american college student, convicted then acquitted of murder in italy. And tonight, facing the possibility of still another trial. She's written a book that comes out today. Later tonight in our one-hour special, we're going to tell you what she says about that strange behavior after the murder, the video kissing her boyfriend, the report that she did cart wheels at the police station. But next the devastating lie she was told during all those years during an italian prison. Capanne prison, 500 prisoners, in a tiny room, a 22-year-old american girl sentenced to 26 years, said at night she could hear women wailing in their cells. You wrote, I felt as if i were being sealed into a tomb. Yeah. And the took was my life. It wasn't the prison. It was my life. Did you think about suicide? I did. She writes she considered cutting her wrists in the shower or swallowing bleach. She says she had panic attacks, began to lose her hair. And one day a doctor called her in to say he had more bad news. They had analyzed the blood sample from the day she arrived. And the doctor told me that i had tested positive for hiv. I was stunned. I went back to my room with one of the prison officials telling me, well, you should have thought about it before you had sex with all those people. She made a list of the seven sexual encounters of her life. And they leaked it? They leaked it to the media. Afterwards, incredibly, they tell knox it was all just a mistake. She wasn't hiv-positive after all. She writes that what will save her in prison are small acts of humanity. And visits from the family she loved, who mortgaged their homes and traveled 6,000 miles to be near her. I felt incredibly guilty for what they were having to sacrifice for me. And there was a certain point in my -- in my thinking in prison that if it didn't work out and i never was free again, I was trying to figure out how I could ask them to move on with their life without me. Because I was tired of them having to sacrifice everything for me. Everything. It is a riveted story. And as we said, there will be so much more tonight in our one-hour special, murder mystery, amanda knox speaks, tonight 10:00 p.M. Eastern, an abc news exclusive.
This transcript has been automatically generated and may not be 100% accurate.