Dr. Cal Lightman is the founder of The Lightman Group, a private consulting company specializing in deception detection. The character is loosely based on Dr. Paul Ekman, the inspiration for the series. Through years of psychological research, Dr. Lightman has become somewhat of a “human lie detector”, and uses these skills to assist in investigations with local and federal law enforcement. Though founded in his own research, many of his tactics are unconventional. He often comes off as rude or abrasive as he will stop at almost nothing to get to the truth.

Tim Roth, born Timothy Simon Roth on May 14th 1961, is an English actor and director, and the star of Lie To Me. Roth first gained attention for various british roles in the 1980s and later gained international recognition for appearing in a variety of Quentin Tarantino Films (including Reservoir Dogs, Pulp Fiction, Four Rooms, and The Hateful Eight). Roth won the BAFTA award for best actor in a supporting role for his part in the historical drama Rob Roy, and was also nominated for the Academy Award for best supporting actor for this same role. Roth made his directorial debut in 1996 with The War Zone, during which time Roth revealed that he is a survivor of child sexual abuse, a topic the film deals with. Roth has married twice and has three children.