Josh Hartnett studied serial killers for his latest movie role. The 46-year-old actor made his name in the late 1990s on the drama series ‘Cracker ‘ and then starred in a string of comedies like ’40 Days and 40 Nights’ but revealed that he delved into the world of murder to play a serial killer in his new film ‘Trap’. He told Britain’s HELLO magazine: “Yeah, my character is basically a serial killer. He’s no hero – although he is to his daughter and to those around him. He’s a sociopath with a very, very dark secret. It’s a secret that is suddenly at risk of being exposed when he takes his dau…