Jared Leto spent time with psychopaths who had committed "horrendous crimes" to prepare for his role as the Joker.
The 44-year-old actor will take on the role of the supervillain in upcoming superhero movie Suicide Squad and pulled out all the stops to ensure his version of the character was suitably complex.
Talking about his research, he said: "[I met] people that were experts, doctors, psychiatrists that dealt with psychopaths and people who had committed horrendous crimes ... I spent some time with those people themselves, people who have been institutionalised."
Jared remained in character throughout the filming process and was determined his version of the Joker would go in a "different direction" to that of the late Heath Ledger's portrayal in 2008 motion picture The Dark Knight, and Jack Nicholson's version in 1989's Batman.
He added to Entertainment Weekly: "There had been such great work that we knew we had to go in a different direction."
As well as meeting with psychopaths, Jared sent this co-stars unusual items such as used condoms, anal beads and a dead pig during filming.
He recently said: "I did a lot of things to create a dynamic to create an element of surprise, a spontaneity, and to really break down any kind of walls that may be there. The Joker is somebody who doesn't really respect things like personal space or boundaries."
Will Smith - who plays expert marksman Deadshot - added: "He went full Joker. He really set the tone. He wasn't playing with it. He was dead serious as an actor. He was going in and he was 100 per cent going into this character."
Margot Robbie, Joel Kinnaman, Viola Davis and Jai Courtney are also set to star in the movie.
- Bang! Showbiz