Lightman believes the student of his mentor is a psychopath in the episode "Beat the Devil." He tries to convince her of that here.
Jason Dohring guest stars on the 6/7/10 episode of Lie to Me. He plays a suspicious graduate student who Lightman must investigate.

Lie to Me Season 2 Episode 11 Quotes

Ria Torres: You really want to take this case?
Eli Loker: What, is the guy and eccentric? Yes, big time. But so am I, have you seen this shirt.

Here's the problem, Martin Walker is a psychopath and probably a killer. Just though you should know.

Cal Lightman