Speaking to “Star Wars” fan site The Tattooine Times, Gillard called the Anakin & Obi-Wan vs Dooku duel “our most complicated [lightsaber fight].” It makes sense why they wanted to give it such a memorable ending. Gillard recounted:
“We wanted to chop [Dooku’s] head off … that wasn’t in the script, but we thought it needed to be that brutal. Dooku technically should have known he was going to lose. I mean, we tried to show it through the fight that suddenly he’s thinking ‘Oh my god, this kid is something else, I’m in trouble’, but I don’t know if that came across.”
Gillard isn’t just being edgy here; Dooku’s death is not supposed to feel victorious. It’s the film’s first taste of Anakin giving into his rage, the first scene where we see him set foot on the path to becoming Darth Vader. It’s all but said that Anakin specifically chose to cut off Dooku’s arms because the Count robbed him of his own right hand in “Attack of the Clones.” Such a vengeful act is not the Jedi way, and Anakin expresses regret once Dooku’s head hits the floor. Unfortunately, Palpatine is there to transmute Anakin’s guilt into triumph.
Now, “Revenge of the Sith: Illustrated Screenplay: Star Wars: Episode III” does describe Dooku as being decapitated by Anakin. However, that book also acknowledges the script was often rewritten. If Gillard’s recollection is correct, it’s possible that George Lucas added the nature of Dooku’s death to the shooting script.
Said script declares, “Anakin cuts off Count Dooku’s head.” Since scripts are ultimately blueprints, you have to be economical about detail — directors and actors can add depth later. “Revenge of the Sith” had someone who was more than capable of doing so in Sir Christopher Lee.