"I question whether the respect given to our findings of fact based on the demeanour of the witnesses is always deserved. I doubt my own ability, and sometimes that of other judges, to discern from a witness's demeanour, or the tone of his voice, whether he is telling the truth. He speaks hesitantly. Is that the mark of a cautious man, whose statements are for that reason to be respected, or is he taking time to fabricate? Is the emphatic witness putting on an act to deceive me, or is he speaking from the fullness of his heart, knowing that he is right? Is he likely to be more truthful if he looks me straight in the face than if he casts his eyes on the ground perhaps from shyness or a natural timidity? For my part I rely on these considerations as little as I can help." "
"Psychologists and other students of human communication have investigated many aspects of deceptive behavior and its detection. As part of this investigation, they have attempted to determine experimentally whether ordinary people can effectively use nonverbal indicia to determine whether another person is lying. In effect, social scientists have tested the legal premise concerning demeanor as a scientific hypothesis. With impressive consistency, the experimental results indicate that this legal premise is erroneous. According to the empirical evidence, ordinary people cannot make effective use of demeanor in deciding whether to believe a witness. On the contrary, there is some evidence that the observation of demeanor diminishes rather than enhances the accuracy of credibility judgments."