Since his impeachment, President Clinton has been the focus of study after study about detecting truths and untruths in sworn testimony.
But for the professionals who are best at detecting even a well-trained liar, one need look no further than the agency assigned to protect the president, the U.S. Secret Service.
More than sheriffs, small-town police officers, psychologists and even judges, agents of the Secret Service show the greatest capacity to distinguish truth from untruth, says the author of one recent study.
The ability of certain professions to tell truth from lies was examined in "A Few Can Catch a Liar," a study published last month in "Psychological Science," a journal of the American Psychological Society.
One of the authors, Paul Ekman, psychology professor at UC San Francisco, began studying liars nearly 30 years ago, when the psychiatric residents he was teaching at the university asked for guidance.
"Many of them had heard of incidents in which patients would deliberately lie, be released for a weekend pass, and then go out and take their own life," said Ekman, who is in London on leave writing a book about emotions. "I thought that was a very practical question, and it raised basic issues about how well we can conceal our emotions."
Ekman thought it would be helpful to examine jobs, such as law-enforcement agents and psychologists, where the ability to discern the truth is particularly valuable.
Most of the study's participants did about as well as one would do if one just guessed, Ekman said. People in the CIA, and some Los Angeles County sheriffs, scored relatively high, but not as high as Secret Service agents have scored in past studies.
The study of lying has been fascinating in its scope, he said.
"It initially surprised me when I began examining lies that they occur in every arena of life," he said. "Once you begin to look, there's no arena in which lies don't occur."
In the study, 20 men ages 18 to 28 were asked to discuss in an interview a belief that they hold true about random social issues. Some were asked to speak truthfully. Others were asked to lie. In earlier studies researchers feared the results were inaccurate because participants had no stake in the outcome of whether they were believed. So this time, researchers sweetened the pot a bit with money.
Truth tellers who convinced their interrogators--male and female--that they were honest got a $10 bonus. Liars who were believed got a $50 bonus. Failed attempts to convince interrogators were not rewarded.
Ekman said upping the ante increases the likelihood of making a lie believable.
Observers were told that at least some of the speakers were lying.
Their decisions were based on actual observation, not mechanical lie detectors of any sort.
Among the groups observed were agents from the CIA, Los Angeles County sheriffs, municipal law enforcement officers, federal judges, and psychologists both clinical and academic. Academic psychologists proved the least effective in telling truth from fiction, surpassed only slightly by clinical psychologists.
In a previous study when Ekman focused on college students, one subject was exceptionally good at detecting lies. When the professor discussed the student's career goal, the answer was "the U.S. Secret Service." James Mackin, a Secret Service special agent based in Washington, says his organization's penchant for discerning the truth is a combination of training and selection.
"We have, unlike other agencies, a dual focus," Mackin said. "We concentrate on criminal activities, like counterfeiting and credit card fraud and cell phone fraud, and we end up doing interviews for that on the criminal side.
"On the other side, we also talk to a wide range of people with a wide range of backgrounds in regard to our protection mission."
As Ekman said, Secret Service agents are "always looking for a needle in a haystack in a crowd, and that would increase their alertness." Certainly, when the stakes are the life of a dignitary, agents are motivated to recognize truth--or the shifty character in who might create havoc or harm their charge, he said.
Other authors of the study were Maureen O'Sullivan of the University of San Francisco and Mark G. Frank of Rutgers, the State University of New Jersey.