Hayden Panettiere on Amanda Knox

Hollywood star Panettiere stars as Knox in a controversial US made-for-TV movie about the murder, set to debut tonight.

And after studying the case for the role, the Heroes actress says she is baffled about what really happened in the Italian case.

She said: 'One of the things that is so interesting and compelling about this story is that you really don't know.

'I spent five weeks over there researching it over and over again, watching any video of her I could get my hands on, any of the [TV] specials that proved different sides, the Italian version compared to the American version.'

Panettiere, 21, told US talk show Live With Regis & Kelly: 'So I'm really torn.

'I'm not even just saying that because I'm not supposed to have an opinion. Genuinely, I have no idea.'

Knox, 23, was charged in December 2009 with the 2007 murder of her roommate, Meredith Kercher in Perugia. She is serving a 26-year sentence in an Italian prison but is appealing her conviction.