Liars do not avert their eyes in an interview on average any more than people telling the truth do, researchers report; they do not fidget, sweat or slump in a chair any more often. They may produce distinct, fleeting changes in expression, experts say, but it is not clear yet how useful it is to analyze those.
Nor have technological advances proved very helpful. No brain-imaging machine can reliably distinguish a doctored story from the truthful one, for instance; ditto for polygraphs, which track changes in physiology as an indirect measure of lying. ...
Still, forensic researchers have not abandoned the search for verbal clues in interrogations. In analyses of what people say when they are lying and when they are telling the truth, they have found tantalizing differences.
Kevin Colwell, a psychologist at Southern Connecticut State University, has advised police departments, Pentagon officials and child protection workers, who need to check the veracity of conflicting accounts from parents and children. He says that people concocting a story prepare a script that is tight and lacking in detail.
“It’s like when your mom busted you as a kid, and you made really obvious mistakes,” Dr. Colwell said. “Well, now you’re working to avoid those.”
By contrast, people telling the truth have no script, and tend to recall more extraneous details and may even make mistakes. They are sloppier.
--Benedict Carey, NYT, on detecting lies