Tatum stars in Side Effects as a recently released criminal who seeks a psychologist's (Jude Law) help to cure his wife (Rooney Mara) of depression with a controversial medication.
Speaking to Flicks and Bits, the actor revealed that he enjoyed playing a deeply conflicted character.
"Not many people come knocking on my door for a white collar crime sort of guy, that's for sure," Tatum said. "Steven felt I would lend the story a different perspective, as opposed to casting somebody we've seen play similar parts a bunch of times."
He continued: "[My character] Martin is a guy who's so competitive. He wanted it all and took it, he convinced himself that it wasn't cheating, it's not stealing.
"And with Emily (Mara), he fell in love with the idea of an innocent, fragile flower he could put on a pedestal in a castle. She's another trophy he won. I think he's got wrapped up in 'winning'. You can easily fall down a slippery slope with that."
Tatum went on to explain that it took a lot of preparation for him to play such a dark character.
"I went to go and meet a bunch of these guys, because I didn't know any traders," he recalled. "I didn't know any guys who had studied that type of thing. But I realised I couldn't play them, it would have taken away from the story.
"I think my character needed to be slightly more sentimental or emotional, or at least more emotionally available to Emily. So eventually I went back to the script, and the back-story."
Side Effects - which also stars Catherine Zeta-Jones and Vinessa Shaw - opens on Friday (February 8) in the US and on March 8 in the UK.
Watch a trailer for the film below: