`The Lightman Group' headed by Dr. Lightman (played brilliantly by Tim Roth) is a team of Lie / Deception specialists who work for government and companies.
The character Dr. Lightman is loosely based on the pioneer of emotions (microexpressions - or nonverbal communication) studies, Dr. Paul Ekman. Ekman is considered as one of the 100 most eminent psychologists of the last century. He proved what Darwin claimed centuries ago by studying several year tribes in Papua New Guinea: facial expressions associated with some emotions are basic or biologically universal to all humans (source: Wikipedia).
In the special feature, Dr. Ekman says something I can support 100%: the series explains many important aspects of human emotions in a couple of seconds while it takes you hours to understand it while reading a book. The makers of Lie to Me did an outstanding job in explaining microexpressions to the audience (including those who had never heard of it).