There has been a common assumption throughout human history and across cultures that liars give themselves away through obvious bodily changes: having a flushed faced, avoiding eye contact, fidgeting, and showing a decrease in salivation.

To take advantage of this behavioral manifestation and to make lie detection objective and scientific, William M. Marston invented the first lie detector around 1917.   He claimed to be able to detect verbal deception by using a machine to measure an increase in systolic blood pressure.

However, his procedure was negatively evaluated in 1923 in a landmark court case known as Frye V. United States.   The defendant James T. Frye was convicted of murder, and he appealed on the basis that the court had not allowed an examiner to testify about the results of a "systolic blood pressure deception test" that he had taken and passed.  The Federal circuit court examined the case and upheld the conviction, articulating what came to be known as the "Frye Test."  The court decided that the thing from which any expert testimony is deduced must be "sufficiently established to have gained general acceptance in the particular field in which it belongs." 

The Frye test was meant to prevent the unfair exploitation of expert witnesses and to ensure the reliability of such testimony.  Since juries may give undue weight to the idea that a "scientist" is testifying and since the information the expert supplies may be over the heads of the jury, they could easily and unknowingly make a bad decision based on something that is not really scientific.  Frye recognized that the fact finders weren't always in a position to assess the validity of claims that were made, and the Frye decision meant that this type of assessment was left to the relevant scientific community who would dispassionately test a new procedure or theory.  Novel or experimental evidence was thus excluded in court until such time as a pool of experts has proven its value.  If there is any significant dispute within the community about the principles upon which the evidence is based about which someone is testifying, the court will not admit the testimony.

At that time, the polygraph was new and had not gone through much objective testing.  Experts had little ground for claiming its reliability or validity.

This Frye Standard became general practice in most courts for many years, effectively preventing judges from running mini-trials about the scientific evidence itself.  While it came in for its share of critics, it was not superseded until 1975 with the Federal Rules of Evidence, and later the 1993 Daubert standard.  It was this latter decision that opened the door in many courts for re-evaluating the scientific status of polygraph results.

Nevertheless, people who believed in physiologically-based lie detection continued to develop techniques.  A more solid procedure was introduced by police officer John Larson.  He built a machine that simultaneously measured pulse rate, blood pressure, and respiratory changes during an interrogation, and he claimed to get very good results.  The problem was that fear, anger, and other emotions are similar to the kinds of reactions that many people have when they lie.  Thus, if a person being questioned is merely upset or nervous, the measurement might indicate the type of emotion that accompanies lying when in fact that person is telling the truth.

Larson then set about developing an interviewing technique, which is called the R/I (relevant/irrelevant) procedure.  Throughout questioning, he would sprinkle questions relevant to the crime ("Do you own a .38 revolver?") and questions that had nothing to do with it ("Are you twenty-eight years old?").  The assumption he made was that the innocent would have a similar physiological response to both types of questions, but guilty people would react more strongly to crime-relevant questions.  The key problem with this approach was that even innocent people might be nervous and crime-specific questions are generally fairly obvious.

Nevertheless, the law enforcement community embraced the polygraph as a device for questioning suspects, even though until 1950, there was only one objective study done to test its scientific validity.

Leonarde Keeler (CORBIS)