A comprehensive 2003 review by the National Academy of Sciences of existing research concluded that there was "little basis for the expectation that a polygraph test could have extremely high accuracy.
[4][5] The cumulative research evidence suggests that machines do detect deception better than chance, but with significant error rates[6] and that strategies used to "beat" polygraph examinations, so-called countermeasures, may be effective.
[8] In 1983 the U.S. Congress Office of Technology Assessment published a review of the technology[6] and found: In the 2007 peer-reviewed academic article "Charlatanry in forensic speech science", the authors reviewed 50 years of lie detector research and came to the conclusion that there is no scientific evidence supporting that voice analysis lie detectors actually work.
[10] Lie detector manufacturer Nemesysco threatened to sue the academic publisher for libel resulting in removal of the article from online databases.
William Moulton Marston studied blood-pressure and noted increase in systolic blood pressure of 10 mm Hg or over indicated guilt through using the tycos sphygmomanometer, with which he reported 90–100% accuracy.
Marston determined systolic blood-pressure by oscillatory methods and his findings cite definite changes in blood pressure during the deception of criminal suspects.
In 1921, John Augustus Larson criticized Marston's intermittent blood pressure method because emotional changes were so brief they could be lost.
To adjust for this he modified the Erlanger sphygmograph to give a continuous blood pressure and pulse curve and used it to study 4,000 criminals.
[15] In the 1990s, a team of scientists, Stanley Abrams, Jean M. Verdier and Oleg Maltsev developed a new methodology contributing six coefficients that positively affect the accuracy of the lie detector analysis results.
[17][18][19] Paul Ekman has used the Facial Action Coding System (FACS) and "when combined with voice and speech measures, [it] reaches detection accuracy rates of up to 90 percent."
"[17] More recently evidence has been provided by the work of CA Morgan III and GA Hazlett that a computer analysis of cognitive interview derived speech content (i.e. response length and unique word count) provides a method for detecting deception that is both demonstrably better than professional judgments of professionals and useful at distinguishing between genuine and false adult claims of exposure to highly stressful, potentially traumatic events.
[21] Another issue is that, due to how the CQT is administered and how the lie-detection process works, only people who are determined to be deceptive are further interrogated for a confession.
[21] While it could be said that including this test as a police tool is useful because it might sometimes provide accurate information, the probability of it causing undue hardship to people who are actually innocent, and wasting time in the process, makes this a very unreliable method for law enforcement officers to use.
Various techniques (which can be found online) can teach individuals how to change the results of the tests, including curling the toes, and biting the tongue.
[26] People have found ways to try and cheat the system, such as taking sedatives to reduce anxiety; using antiperspirant to prevent sweating; and positioning pins or biting parts of the mouth after each question to demonstrate a constant physiological response.
"[29] Several studies published in peer reviewed journals showed VSA to perform at chance level when it comes to detecting deception.
"[3]: 168 People often evaluate lies based on non-verbal behavior, but are quick to place too much merit in misleading indicators, such as: avoidance of eye contact, increased pauses between statements, and excessive movements originating from the hands or feet.
[37] John Kircher, Doug Hacker, Anne Cook, Dan Woltz and David Raskin have developed eye-tracking technology at the University of Utah that they consider a polygraph alternative.
[2] As there are different styles of lying, a spontaneous or artificial deception is constructed based on a mixture of information already stored in semantic and episodic memory.
Recent developments that permit non-invasive monitoring using functional transcranial Doppler (fTCD) technique showed that successful problem-solving employs a discrete knowledge strategy (DKS) that selects neural pathways represented in one hemisphere, while unsuccessful outcome implicates a non-discrete knowledge strategy (nDKS).
Cognitive polygraphy based on this system is devoid of any subjective control of mental processes and, hence, high reliability and specificity; however, this is yet to be tested in forensic practice.
[39] Machine learning algorithms applied to EEG data have also been used to decode whether a subject believed or disbelieved a statement reaching ~90% accuracy.
Understanding how the brain assesses the veracity of a descriptive statement may be an important step in building neuroimaging based lie detection methods.
[40] Functional magnetic resonance imaging looks to the central nervous system to compare time and topography of activity in the brain for lie detection.
While a polygraph detects changes in activity in the peripheral nervous system, fMRI has the potential to catch the lie at the 'source'.
The fMRI scanner then detects the different pulses and fields that are used to distinguish tissue structures and the distinction between layers of the brain, matter type, and the ability to see growths.
[42] Historically, fMRI lie detector tests have not been allowed into evidence in legal proceedings, the most famous attempt being Harvey Nathan's insurance fraud case[43] in 2007.
[28] The lack of legal support has not stopped companies like No Lie MRI and CEPHOS from offering private fMRI scans to test deception.
[28] Truth drugs such as sodium thiopental, ethanol, and cannabis (historically speaking) are used for the purposes of obtaining accurate information from an unwilling subject.
[44] Information obtained by publicly disclosed truth drugs has been shown to be highly unreliable, with subjects apparently freely mixing fact and fantasy.