A very important sort of skepticism:
Police thought that 17-year-old Marty Tankleff seemed too calm after finding his mother stabbed to death and his father mortally bludgeoned in the family’s sprawling Long Island home. Authorities didn’t believe his claims of innocence, and he spent 17 years in prison for the murders.
Yet in another case, detectives thought that 16-year-old Jeffrey Deskovic seemed too distraught and too eager to help detectives after his high school classmate was found strangled. He, too, was judged to be lying and served nearly 16 years for the crime.
One man was not upset enough. The other was too upset. How can such opposite feelings both be telltale clues of hidden guilt?
They’re not, says psychologist Maria Hartwig, a deception researcher at John Jay College of Criminal Justice at the City University of New York. The men, both later exonerated, were victims of a pervasive misconception: that you can spot a liar by the way they act. Across cultures, people believe that behaviors such as averted gaze, fidgeting and stuttering betray deceivers.
In fact, researchers have found little evidence to support this belief despite decades of searching. “One of the problems we face as scholars of lying is that everybody thinks they know how lying works,” says Hartwig, who coauthored a study of nonverbal cues to lying in the Annual Review of Psychology. Such overconfidence has led to serious miscarriages of justice, as Tankleff and Deskovic know all too well. “The mistakes of lie detection are costly to society and people victimized by misjudgments,” says Hartwig. “The stakes are really high.”
The biggest study I've seen of human lie detection found that people were right 54% of the time, which was statistically significant but not exactly proof beyond reasonable doubt. Studies in which police detectives are shown videotapes of actual criminal suspects under interrogation, and asked to judge which statements are true or false, come in somewhere between 64% correct and no better than chance.
The belief that some people are good at detecting liars, or that certain techniques ("microexpressions") will allow anyone to do so, is ancient, and constantly being updated with new types of pseudoscience. But it is wrong.