TORONTO -- Colin Firth doesn't believe in impersonation.
Not for his Oscar-winning performance in "The King's Speech," nor for his latest real-life role as an Arkansas investigator in the West Memphis Three drama, "Devil's Knot."
The British actor says he was more interested in capturing the intellect and spirit of Ron Lax for the Atom Egoyan feature, which traces the mysterious killings of three boys in 1993 and the controversial convictions of three teens in their deaths.
Doing an impersonation holds no interest, Firth said at the Toronto International Film Festival, where the film debuted Sunday.
"I made very little conscious attempt to do that at all," Firth said while sipping coffee at a downtown hotel, wearing a dark suit, white dress shirt and black-rimmed glasses.
"I don't think there's any need ever to do that if you're not playing a character that's recognized to the public."
Firth says he certainly didn't look like Britain's King George VI for "The King's Speech," the 2010 crowd-pleaser about the monarch's sudden ascension to the throne and the speech therapist who helped him overcome a persistent stammer.
"I had a certain amount of freedom not to just be slave to an impersonation," said Firth, noting that the king's features were not widely known to the general public. "And with Ron Lax I didn't have to worry about that at all, but I absorbed something in listening to him."
The persistent work of Lax, and key evidence he discovered, partly led to the release of Damien Echols, Jessie Misskelley Jr., and Jason Baldwin after 18 years in prison.
Firth says he spoke with Lax on the phone in preparation for the role, while Baldwin, the mother and sister of Echols, and Pam Hobbs, the mother of eight-year-old victim Stevie Branch, met with the cast to share their experiences.
Reese Witherspoon plays the devastated Hobbs, who, in the film, harbours growing doubts about the prosecution's case as troubling details emerge.
The sprawling broader cast includes Mireille Enos of "The Killing," Stephen Moyer of "True Blood" and Elias Koteas of "Combat Hospital."
"Devil's Knot" reunites Firth with Egoyan after the two paired for the 2005 mystery "Where the Truth Lies."
Firth says he joined the project because of "The Sweet Hereafter" director, noting he's always liked Egoyan's work.
"I think we have a connection, we enjoy each other's company," he says of their relationship.
"And I like the way his mind works. He's not a linear or conventional thinker. He's maintained his independence, that's not an easy thing to do to when you have success with things. He's very highly regarded, he could have been tempted away by cash and possibility of other opportunities and other ponds to conquer but I think he's maintained a great deal of integrity."
Firth has also come away from the project as a great admirer of Lax, noting he was especially impressed by the investigator's willingness to surrender his story to a dramatic interpretation.
"He gave me absolute freedom to do it however I felt and he was very helpful in terms of his background and his principles and what it was that motivated him," he says.
"I felt great respect for him in that. He has subsequently seen the film and been incredibly positive about it and perhaps most significantly, reported that his wife had authenticated my interpretation. Which, you know, if you can convince the person close to them then that's basically just all I need."
The Toronto International Film Festival runs through Sept. 15.
