Do lie detectors lie?

In the movie “Meet the Parents,” prospective groom Ben Stiller is first interrogated and then polygraphed by his soon to be father-in-law and former CIA spy catcher, Robert De Niro. He then provides the details of Stiller’s life to the prospective bride, in this case De Niro’s daughter.  De Niro’s character was said to be a human lie detector, although he used a conventional (and now outdated) analog polygraph instrument.

Early attempts at figuring out the truth
Long before modern day polygraphs existed, the ancients still had to deal with lies and liars, and their courts had to discern between truthfulness and falsehoods. Trial by ordeal became the order of the day and the “scientific” method of determining truth. 

There were really three original ways of playing “Truth or Consequence”:

1. Trial by fire— this requires the person being tested to walk barefoot over red hot iron. If they survived that and if their wounds healed after three days, they were considered innocent.  
2. Trial by ordeal— the person being tested to plunge his or her arm into boiling water. If they had no blisters, they were assumed to be innocent. A variant on the water theme has the subject of the trial thrown into a river. If he sank he was considered innocent.  (Question: What if he sank and wasn’t recovered— innocent or guilty?) 
3. Last is a somewhat more gentle method to determine truth from fiction: eating food containing a feather. If he choked, you were assumed guilty. This was long before the Heimlich maneuver, therefore if you choked, you might also be dead!

The earliest recorded attempt to invent a machine that separated truth from fiction was in 1895, but it was not until 1915 that a device was developed that established the correlation of blood pressure and respiratory changes with lying.

In 1921, an instrument capable of continuously recording blood pressure, respiration, and pulse rate was devised, followed by the first polygraph in 1926. Later versions have followed, but these machines still rely on the premise that there is a correlation between truth, lies, and body response.

How it works
A polygraph does not really separate truth from lies; or the honest from the liar. It simply provides information concerning any change in physiological response in areas such as respiration, heartbeat and blood pressure, this while the person being tested undergoes questioning. 

As a retired FBI agent, I don’t want to take anything away from my former law enforcement colleagues who practice the art (vs. science) of detecting truth, but I have been less than confident in the statistical success rate of the polygraph, having seen killers “pass” the test, and honest people “fail.”

You see, the prevailing theory behind the polygraph is that when someone tells a lie, they become nervous about their lies and their nervousness causes changes that can be noted in their breathing, their heartbeat, their perspiration and their blood pressure.  An initial baseline is established by asking questions of the person being tested whose correct answers are known to the polygraph operator (or forensic psychophysiologist).  Deviation from the known baseline for truthful answers is then taken as an indication of deception.

But what about psychopaths, sociopaths or just damn good liars?  If the old adage is correct, i.e., “If you believe it yourself it then passes as truth,” or if you have learned to control of your bodily reactions, why can’t you “pass” a lie detector test even if you are “lying?”

RELATED INFO Aldrich Ames beat the machine One of the most prolific and damaging spies that hid within halls of the CIA was Aldrich Ames. As a mole for the Russian KGB, he earned $3 million dollars by providing the Soviets with information that caused the deaths of more than a dozen U.S. intelligence operatives throughout the former USSR and elsewhere. Ames provided the Russians with information that not only cost lives, but millions of dollars in research that had been spent by the U.S. and then acquired by Moscow for fractions of a penny on the dollar.  Ames was able to accomplish his classic acts of treason while passing every routine agency polygraph test that he encountered with flying colors— not to mention that his lifestyle, clothing, vehicles and his home should have set off bells and whistles far louder that the hum of a polygraph machine. But just as he passed the polygraph, he just as easily slid past the common sense test of unexplained affluence on the part of a government employee.

And what about the opposite: What if you are completely innocent but nervous, angry, sad, embarrassed or just fearful of a test whose results may affect your entire life?  Or what if you have a cold, a muscular problem, a headache, or if you’re simply constipated?  Can these purely non-voluntary bodily symptoms or conditions affect the physiological changes that are being measured against “the truth baseline?”  And what if you are nervous?  Is the nervousness due to the fact that you know you’ve done something wrong and may get found out by the polygraph, or are you simply nervous for any number of other reasons— all totally unrelated to your complicity in some suggested criminal act?

The ACLU, an organization with which I do not normally side, supported the passage of the 1988 Employee Polygraph Protection Act that outlawed the use of the polygraph “for the purpose of rendering a diagnostic opinion regarding the honesty or dishonesty of an individual.” 

Does the polygraph, in the hands of a trained, competent individual really allow the operator to detect deception on the part of the person being tested?  Well, yes and no. Try betting your life or your career on that one!      

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