"Baby Oliver" was cast before he was even born. The producers chose a woman who was pregnant with twin boys who would deliver about the time filming began so the baby would genuinely be a newborn baby, as his character is.
One of the rules that Michael Davis observed was that there would be no explosions. Every scene had to be gun-centric.
Paul Giamatti's first experience of handling a firearm. Both he and Clive Owen attended a gun school to familiarize themselves with how to handle various weapons.
Monica Bellucci, who is a polyglot, dubbed herself for the Italian and the French versions of the film.
The actress who gets spanked by Mr Smith because he sees her spanking her child was very excited about the prospect of being spanked by Clive Owen.