Where did you get the idea for your most recent book?
I went to an exhibition of death masks at the Musée d’Orsay in 2001. Apart from the casts made of people’s faces after they’d been executed, there were some casts of the hands of murderers. I was researching another novel at the time and found a book on the new extension to the Palais de Justice in Paris. The first case trailed in the new court was the Troppmann case and the book had a photo of a cast of his hand. I found that intriguing and started looking for more books on the case. Once I started, I was less and less convinced of his guilt.