LOS ANGELES, California (CNN)  -- Actor Tim Roth is in an abandoned building near downtown Los Angeles, and he's about to mix things up.



British actor Tim Roth plays a human lie detector on the hit series "Lie to Me."



"This is a scene where the FBI is interrogating a suspect," Roth said. "I'm breaking into the interrogation to get information out of him using the sort of techniques that my character espouses as opposed to pressuring him."



Roth, who plays Dr. Cal Lightman on the hit Fox series "Lie to Me," is shooting scenes for the season finale, which will air May 13. His character is an expert on body language and the detection of deception.



"Our series is based on the idea that we can read what's going on across your face and if it's contradicting what you're actually saying," Roth said.



Lightman and his colleague, Dr. Gillian Foster -- played by Kelli Williams -- run "The Lightman Group."



They observe body language and interpret what it means in order to help law enforcement agencies see through the bull.



His character is based on Dr. Paul Ekman, a specialist who reads clues embedded in the human face, body and voice to expose the truth in criminal investigations.



Ekman, who in 2001 was named as one of the most influential psychologists of the 20th century by the American Psychological Association, is a scientific consultant for the show.



Roth says Ekman can be intimidating.



"He makes me very, very nervous, Paul, you know," he said. "I mean, he's the sweetest man, as sweet as can be, but when he's around, you feel like your acting is really being judged."



Roth is perhaps best known for his outings with famed director Quentin Tarantino. The British actor pulled off a convincing American accent in the cult classics "Reservoir Dogs" and "Pulp Fiction."



He uses his true-Brit accent in "Lie to Me," which debuted in January and is one of the season's few successful new dramas.



In a review for Entertainment Weekly, critic-at-large Ken Tucker wrote that "Like 'Monk' and 'Psych' and 'The Mentalist,' 'Lie' offers us an eccentric who's brought in by law enforcement to solve crimes."



Though he gave the show a B-minus, Tucker praised Roth for "resist[ing] the cuddly/cranky."



The show has quickly found its fan base, though ratings have declined slightly since the show was put in its 8 p.m. Wednesday time slot, ahead of "American Idol." (The first five episodes aired after "Idol.")



"I got stopped because one of my lights was out and I was coming back from work and the guy, the cop that stopped me said 'Oh, we watch your show' and they seemed to enjoy it," said Roth.



"ER" alum Mekhi Phifer is set to join the cast as an FBI agent for two episodes this season, starting Thursday.



"I'm here to kick ass and take names, you know. So it's kind of different," Phifer said. "It's fun, you know. Obviously, I carry a gun and I'm in law enforcement rather than being a doctor."



Phifer particularly likes acting in intense scenes with Roth.



"I have my own way of doing it," he said. "It's a little different than the way Tim does it. It's a lot of fun, and we're having a great time."



And will time spent on the show help Phifer better detect when people are lying to him in real life?



"It's going to take a few more episodes, but I'm pretty perceptive," he said.



Roth, however, makes no claims of special powers -- at least when he's away from the set.



"I try not to know too much, because it
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