All liars have viewable "tells".

• Position: Interrogation - Brief article

Carolyn Hurley, a research scientist for the U.S. Transportation Security Administration, has spent a lot of time studying the faces of people lying when in high-stakes situations and has good news for security specialists. A study she was lead author on reports that, although liars can reduce facial actions when under scrutiny, they cannot suppress them all.

The results are derived from frame-by-frame coding of facial movements filmed during an interrogation in which participants, some lying, some telling the truth, were asked to suppress specific parts of facial expressions. Hurley found that these actions can be reduced, but not eliminated, and that instructions to the subjects to suppress one element of expression results in reduction of all facial movement, regardless of their implications for veracity.

Despite these findings...