Oscar-winner Colin Firth has been cast opposite Reese Witherspoon in "Devil's Knot", the forthcoming West Memphis Three film that's being directed by Atom Egoyan ("Chloe", "The Sweet Hereafter"). The British actor will play Ron Lax, a private investigator who lent his services on behalf of defendants Damien Echols, Jason Baldwin and Jessie Misskelley during their original trials. Though he ultimately uncovered many details that pointed to the innocence of the trio, who came to be known as the West Memphis Three, his efforts weren't enough to keep them from being convicted of murder and sentenced to either life in prison (Baldwin and Misskelley) or, in Echols' case, death.

Witherspoon was cast back in December as Pam Hobbs, the mother of murder victim Stevie Branch. Though she was initially convinced of the three teens' guilt in the crime, she later came to doubt their involvement.

The Firth news was broken by Deadline.

"Devil's Knot" comes in the wake of several previous documentaries made about the case, including Joe Berlinger and Bruce Sinofsky's "Paradise Lost" trilogy and the Peter Jackson-produced "West of Memphis", which premiered at the Sundance Film Festival earlier this month.

Echols, Baldwin and Misskelley were released from prison last August on an Alford (read: technically guilty) plea, a legal maneuver that allowed them to assert their innocence while still admitting that if a new trial were to be held, they would likely be convicted based on existing evidence.

Egoyan is aiming to shoot the film this summer in Louisiana, from a script he is currently rewriting with Paul Boardman. Boardman wrote the original screenplay with Scott Derrickson, his partner on the 2005 hit "The Exorcism of Emily Rose" (which Derrickson directed).

How do you feel about the big-name cast being assembled for "Devil's Knot"? Are you glad the case is getting the high-profile treatment, or would you prefer a grittier, less-star-studded take on the story? Sound off in the comments below!