A graduate of Tufts University and the UCLA Film School Niels Mueller scripted the indie hit Tadpole in 2002. Now he has finally made his directorial debut with The Assassination Of Richard Nixon, a story co-written with Kevin Kennedy. It tells the true story of Sam Bicke (played by Sean Penn), who sets in motion an audacious plan to kill the man he holds responsible for everything wrong in his life.

The Assassination Of Richard Nixon highlights a little known historical event Was this what moved you to make a film about it?

When I started writing the story I was interested in writing about an assassin whose assassination attempt isn't noticed. I was actually calling it The Assassination of LBJ, choosing a president who nobody had tried to kill. Then I started my research and after I took a few books out of the LA Public Library, one of them had this very slim chapter on Sam Bicke.

What did you find out about him?

He was very much like the character I was writing about without my realising it. It was at that point that I changed the script from 1964 to 1974, and took out the parts of my story that didn't fit these real events. At the end of the film it says 'Inspired by a true story' but that's really only one lawyer's choice, where another lawyer might have said 'Based on a true story'.

Did you consult with Sam Bicke's family at all during the whole process?

Not until I'd written the script. I spoke to them before we shot it, and showed them the film after we finished it. I think they feel appreciative of the way I handled the subject matter. I always try to give a short answer to this question because we worked really hard to protect issues of their privacy.

Sean Penn delivers another spellbinding performance in the lead. How did you get him involved?

I wouldn't have allowed myself to dream that Sean would do this film and work with a director he'd obviously never heard of. That said, the script was sent to Sean on a Wednesday, he got it Thursday, and called me on the Friday. He said he loved the script and said he'd love to meet me. I flew to San Francisco on the Monday and within a half an hour of the first meeting he said we should make the film. From that point on, Sean was unwavering in his commitment to the film. Every time things fell apart financially Sean would re-commit. He's a rare man of his word in this line of work, a handshake is everything to him. The film got made because of his commitment to the project.

How did you find it actually directing him?

On the first day of production I actually forgot to call cut on the first few takes. I was just watching, thinking, "Wow. There's Sean Penn and Don Cheadle!" Eventually I had to snap out of it and remind myself that I had a job to do. I was pleased at how quickly I was able to start doing what I needed to do. The thought of it is always more intimidating than doing it. I also had a crew that really embraced the film as their own. It was a really great group of people I was able to put together.

And what did you observe of him at work?

I would talk to Sean off the set, and it would be Sean. But then I watched him walk onto the set, enter Sam's apartment, and get into Sam's chair. And suddenly, as we were getting ready to roll, Sean would disappear. One thing I noticed in post production was that any time I called cut! you'd see Sean re-emerging back out of the character. He crosses his legs differently, he walks differently. Sean is as great an actor as he is because he uses everything available to him to inhabit the role. He works through every muscle and pore in his body.

The Assassination Of Richard Nixon is released in UK cinemas on Friday 8th April 2005.