The first time I confronted the unreliability of a lie detection device was when I was a defense attorney. A law enforcement officer informed me that my client was guilty because he had flunked a voice-stress analysis. He said the machine said my client had forged a lottery ticket (the ticket was a small winner), and the machine didn’t lie. Lucky for my client, I didn’t trust the machine and I located witnesses that said that the ticket was forged by others as a practical joke at work. The charges were ultimately dismissed.
As a prosecutor, the detection of lies was an important part of what I did. People were charged, or not charged, based on a credibility determination of the witnesses. Sex crimes were often involved. Was the sex consensual or not? Was there sexual contact or not? Under certain circumstances, I would consider the results of polygraph examinations, along with all other evidence, in making charging decisions. The evidence regarding the efficacy of polygraphs in lie detecting was mixed, but evidence existed to that showed a polygraph result that indicated truthfulness had some reliability.[i]
Polygraph evidence is not admissible in Wisconsin Courts. State v. Dean, 103 Wis. 2d 228, 279, 307 N.W.2d 628 (1981). Anything that a defendant says during a polygraph examination is also not admissible. State v. Schlise, 86 Wis. 2d 26, 42-44, 271 N.W.2d 619, 627 (1978). Statements that a defendant makes after the polygraph examination is over may be admissible. State v. Johnson, 193 Wis. 2d 382, 388, 535 N.W.2d 441, 442-443 (Ct. App. 1995);
State v. Greer, 2003 WI App 112, ¶. Also, an offer to take a polygraph test can be relevant to a defendant’s credibility and may be admissible at trial for that purpose. State v. Pfaff, 2004 WI App 31, ¶26.
I also have experience with computerized layered voice analysis, which is a more sophisticated form of voice stress analysis, which was a technology also used by law enforcement when I was a prosecutor. My opinion is they are about as accurate as voice stress tests.
The problem with all lie detecting devices is that: “There is no evidence that any pattern of physiological reactions is unique to deception.”[ii] Based on my experience, another error can arise because of biased interpretation of the results through confirmation error. The interpreter of the results often find the results that they were looking for in the data.
Newer techniques have been developed with the advent of brain imaging techniques. These techniques are based on theory that there are unique circuits in the brain that may be activated when one lies. A recent study took a look at one of these techniques. The researchers concluded that no one area of the brain was identified as being helpful in detecting deception.[iii] These researchers correctly identified 71% of lying subjects. The researchers stated that the use of a functional MRI is a more direct measurement of what is happening in one’s brain. However, the same problem of identifying a unique pattern of brain activity associated with lying remains.[iv]
If anyone is interested in further research regarding the detection of lies, and a discussion on the research regarding polygraphs, I can recommend a book written by one of the preeminent scholars in the field, Paul Ekman, entitled Telling Lies, Clues to Deceit in the Marketplace, Politics, and Marriage. Ekman discusses, in detail, the challenges in detecting lies. We, as well as jurors, probably have an erroneous confidence in our ability to detect lies.
[i] Ekman, 2001, Paul, Telling Lies—Clues to Deceit in the Marketplace, Politics and Marriage, W.W. Norton & Company, New York, pp. 215-223
[ii] “The Truth About Lie Detectors (aka Polygraph Tests)”, 2004, American Psychological Association.
[iii] Monteleone et al, 2009, “Detection of deception using fMRI: Better than chance, but well below perfection.”, Social Neuroscience, Vol. 4. Issue. 6, pp. 528-538.
[iv] Ibid.
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