The Myth of the Polygraph
Even J. Edgar Hoover knew that the polygraph wasn’t any good for detecting deception. He dropped the test.
The polygraph was invented in 1915 by a Harvard man called William Moulton Marston, who claimed that his clunky little gizmo could detect lies by measuring blood pressure. Marston’s main claim to fame derives not from his machine, but from a doodle he came up with: the cartoon character Wonder Woman.
In the past 85 years, the polygraph hasn’t changed much from the Marston prototype. ”The secret of the polygraph is that their machine is no more capable of telling the truth than were the priests of ancient Rome standing knee-deep in chicken parts,” says Alan Zelicoff, a physician and senior scientist at the Center for National Security and Arms Control at the Sandia Labs in Albuquerque, NM. Zelicoff gave us this view in an article featured in the The Skeptical Inquirer.
He writes that the polygraph administrator is a kind of confidence artist or modern day mesmerist who tries to seduce (or scare) his subjects into believing in the power of the machine to catch them in the most minute inconsistency.
“The subject, nervously strapped in a chair, is often convinced by the aura surrounding this cheap parlor trick, and is then putty in the hands of the polygrapher, who then launches into an intrusive, illegal and wide-ranging inquisition,” Zelicoff writes. “The subject is told from time to time that the machine is indicating ‘deception.’ It isn’t, of course. And he is continuously urged to clarify his answers, by providing more and more personal information.” At an arbitrary point, the polygrapher calls off the testing, consults the spools of graph paper and makes an entirely subjective rendering on whether the subject has given a “deceptive response.”
“Every first-year medical student knows that the four parameters measured during a polygraph–blood pressure, pulse, sweat production, and breathing rate–are affected by an uncountable myriad of emotions: joy, hate, elation, sadness, anxiety, depression, and so forth,” says Zelicoff. “But there is not one chapter–not one–in any medical text that associates these quantities in any way with an individual’s intent to deceive. More importantly, dozens of studies over the past 20 years in psychology departments and medical schools all over the world have shown that the polygraph cannot distinguish between truth-telling and lying.”
Connoisseurs of the Wen Ho Lee affair will remember that at one point the FBI falsely told the Taiwanese nuclear physicist (accused of spying for the Chinese at Los Alamos) that polygraph tests showed he was lying. Cops play these sorts of tricks all the time, faking forensic reports and then shoving them under the nose of their suspect, shouting that he’s a proven liar and that he’d best sign a confession right away.
The most comprehensive review of the polygraph was conducted in 1983 by the Office of Technology Assessment, a research branch of congress. The OTA concluded, “There is no known physiological response that is unique to deception.” The report did note that the CIA and its companions “believe that the polygraph is a useful screening tool.” However, OTA concluded that the available research does not establish the scientific validity of the polygraph for this purpose. The best that OTA could say about the polygraph was that it might have some limited validity in “specific criminal incidents.” But the report went on to observe that in such cases, “the polygraph test detects deception better than chance, but with error rates that could be significant.” As for the supposedly revealing physiological responses, the congressional study reported that they could be masked “by physical movement, drugs or other techniques to avoid detection as deceptive.”
There are numerous ghastly stories of federal employees who were abused by the machine and its operators. Take the case of 19-year Navy veteran Daniel M. King, who was suspected of selling classified information. King was locked up in military prison in solitary confinement for 500 days and subjected to repeated polygraphs. Some of them lasted for as long as 19 hours. A military judge dismissed all the charges against him.
A few years ago FBI agent Mark Mallah was given a routine polygraph. The polygrapher, who had only 80 hours of experience with the machine, concluded that Mallah had lied. (Zelicoff notes that even barbers must have 1000 hours of training before getting a license to cut hair.) His life soon transformed into a Kafka story. He was stripped of his badge, subjected to midnight searches of his house, his diary and appointment book seized and scrutinized, his neighbors, friends and relatives interrogated, his every move outside monitored by helicopters. In the end, Mallah’s life was pretty much destroyed, but nothing was ever proved against him. The FBI finally apologized and Congress outlawed the use of the polygraph for civilian employees in 1988.
It’s worth noting that the Walker brothers and Aldrich Ames both beat the polygraph with no sweat. Kim Philby settled himself with a dollop of Valium before breezing through his polygraph exams.
One investigator for a defense lawyer in California told us that, while the polygraph isn’t admissible in most courts, it’s used all the time by prosecutors, mostly to seal plea bargains. “It’s a perilous option, because the utility of the polygraph is almost totally up to the operator,” she said. “There are good polygraphers, but many who work for the district attorneys have only minimal training.”
The investigator described a recent case where a defense witness in a homicide case, who had passed a polygraph given by a former FBI polygrapher with 20 years of experience, was sent to the DA for another test given by their examiner, a relative novice with the device. Defense lawyers can’t be in the room while the test is given, even when their clients are being examined. The prosecutors videotape the session, and while the results of the polygraph can’t be used at trial, the videotape can become evidence. In this case, the defense lawyer waited in the hall until the witness emerged from the room “with his face red as a beet.” The lawyer heard the DA’s investigator threaten the witness: ”You little slimebag, I know you’re lying. We’re going to revoke your parole.” The DA’s examiner had interpreted the readings from one of his answers as being “deceptive.”
Jeffrey St. Clair is the author of Been Brown So Long It Looked Like Green to Me: the Politics of Nature, Grand Theft Pentagon and Born Under a Bad Sky. His latest book is Hopeless: Barack Obama and the Politics of Illusion. He can be reached at: firstname.lastname@example.org.
This essay is adapted from an article in the July 2001 edition of CounterPunch.