South African beauty Charlize Theron was given a beastly make-over to become the real-life serial killer Aileen Wuornos in Patty Jenkins' directorial debut, Monster. But while Theron's transformation is astonishing, there is far more to her performance than just makeup, false teeth, and an extra 30 pounds in weight: her Wuornos is a fully rounded human being, as vulnerable as she is dangerous. Sympathy for the devil? You be the judge.

Did you push for this role, because you are also a producer on the film?

Patty [Jenkins] came to me. It felt very odd because that had never happened to me before. This is usually the kind of stuff that I read and I love, and I am banging down the door trying to get a meeting, and then trying to prove that I can do it. So I was touched by Patty's trust, and extremely willing to do anything.

How did you get inside Aileen Wuornos?

As soon as we said we were going to do this, we dived straight into Aileen's emotional scene, and it took a while before we started talking about the physical aspect. It became evident to me that everything about her physically was a map to what she had gone through emotionally. She was a woman living in the streets, and if you're going to be this timid little wallflower, you're not going to survive. Aileen was five-foot-three, but when she walked into a room, everything about her changed: her shoulders went back, her head went back. That's somebody who's trying to send the message: "Don't mess with me."

People often see undergoing this kind of transformation as a bid for an Oscar...

Yes, people have made this correlation that if you go 'ugly' you'll win an Academy Award [HEY - IT WORKS!!!]. But the truth of the matter is if the work is good and the work is challenging, it doesn't matter what body it comes in. Here's the thing: it's not personal. It's not about me. I don't sit around thinking people think that that is me 'ugly'. Maybe that is naïve, but that has nothing to do with me. It's a character, you know?

What is your opinion on the death penalty?

I'm not for the death penalty. And, if anything, making this film made me more aware of how ineffective it is. I am a realist. So, for me, if you look at the numbers, it's not working. Also, I struggle with it morally. I don't necessarily think that condemning people who murder and then killing them sends the right message out. Then I have a huge problem with how these people are used as political pawns. I'm quite disgusted by that.

Monster is released in UK cinemas on Friday 2nd April 2004.