Lie Detector and Polygraph Tests: Are They Reliable? | Nolo.com Lie Detector and Polygraph Tests: Are They Reliable? Learn how polygraph and lie detector tests work and whether they are accurate. Share on Facebook Lie detector tests -- or polygraph tests, in more scientific terms -- are rarely used in criminal trials. The theory underlying a lie detector test is that lying is stressful, and that this stress can be measured and recorded on a polygraph machine. Lie detectors are called polygraphs because the test consists of simultaneously monitoring several of the suspect's physiological functions -- breathing, pulse, and galvanic skin response -- and printing out the results on graph paper. The printout shows exactly when, during the questioning period, the biologic responses occurred. If the period of greatest biologic reaction lines up with the key questions on the graph paper -- the questions that would implicate the person as being involved with the crime -- stress is presumed. And along with this presumption of stress comes a second presumption: that the stress indicates a lie.

Arguments For and Against Supporters of lie detector tests claim that the test is reliable because: very few people can control all three physiological functions at the same time, and polygraph examiners run preexamination tests on the suspect that enable the examiners to measure that individual's reaction to telling a lie. On the other hand, critics of polygraph testing argue that: many subjects can indeed conceal stress even when they are aware that they are lying, and there is no reliable way to distinguish an individual's stress generated by the test and the stress generated by a particular lie. The courts in most jurisdictions doubt the reliability of lie detector tests and refuse to admit the results into evidence. Some states do admit the results of polygraph tests at trial if the prosecution and defendant agree prior to the test that its results will be admissible. Are Lie Detectors Telling the Truth? You may wonder how, in the absence of a confession, a polygraph operator can confidently determine whether a person is lying. Don't most people -- even innocent ones -- get stressed when being asked questions that might land them in big trouble? Yes, but the polygraph operator has techniques to overcome this problem. Before getting to the nitty-gritty of the issue ("Did you do it?

Were you there? Do you have any personal knowledge of what happened?") the operator first asks a series of questions, some of which are emotionally neutral and some of which are calculated to cause emotional discomfort based on the test subject's personal circumstances. The subject's physiological responses to these questions are meticulously calibrated. Then, when the operator gets around to the core questions, the responses to those questions can be measured and compared to the responses produced by the neutral and control questions. It's true, a lot of devils can live in the space of relative anxiety measurements, but numerous independent tests have indicated an accuracy rate in the 80-90% range. Fooling a Polygraph So if these tests are so accurate, why aren't they required in every situation where truth is at issue? Why spend billions of dollars on jury trials and independent prosecutors when we could just "wire up" the key witnesses and get at the truth with no fuss and no muss? Some people are so divorced from morality or a guilty conscience that they may test honest -- because they are really good liars or have convinced themselves of a truth that isn't the truth at all.

It may also be possible to change the results through other methods, such as yogic or biofeedback training, the "nail in the shoe" trick (putting a sharp nail in your shoe to cause yourself pain during the questions to skew the polygraph results), or using a legal or illegal drug to calibrate one's emotions. Simply put, there is no way to turn a lie detector test into a slam dunk. For this reason, most courts will not admit polygraph results unless both sides of the case agree. The Straight Dope: How accurate are lie-detector tests? How accurate are lie-detector tests? April 23, 2010 Dear Cecil: What's the effectiveness of a polygraph? Police departments still use them, and the feds still screen applicants using polygraphs, but the U.S. Supreme Court has ruled them invalid. Surely they can't tell if you're lying, and surely not all lies produce the exact same physiological response in every person. — Rob Cecil replies: Lie-detector tests aren't completely worthless. How's that for an endorsement? The polygraph, the most common lie-detection instrument, works on the assumption that the body reacts involuntarily to the stress of lying.

It measures reactions such as changes in skin conductance, pulse rate, blood pressure, and breathing while the subject is asked a series of questions. The questioning process can take several forms. One early version was the "relevant-irrelevant" technique, which mixed queries like "Did you murder [name of victim]?" in with stuff like "Is today Tuesday?" Lies in response to the relevant questions would supposedly make the needles jump. The problem with this approach was that in such a context even an unfounded accusatory question could be stressful, producing a false positive. The "comparison question" technique tries to get around this problem by making all the queries accusatory. In a sex-crime investigation, for instance, a suspect might be asked embarrassing control questions such as "Have you ever committed a sexual act you were ashamed of?" along with questions pertaining more directly to the case. The idea, which has a certain devious ingenuity, is that the innocent will show a greater response to the control questions (either because they're lying or simply flustered), whereas the guilty will show a greater response to the pertinent questions (which for them are more consequential).

The "guilty knowledge" testing method tries to discover whether a subject is privy to inside info about a case — things that only someone involved would know about. For example, suspects might be shown assorted photos of guns to see how they respond to the one that happens to show the murder weapon. Besides investigation of crimes and the like, the other big use for polygraphs is general screening by employers looking to weed out iffy job applicants or catch workers in otherwise undetected wrongdoing. Pre-employment screening is common in law enforcement: one study found nearly two-thirds of agencies administered polygraph exams to applicants and rejected about 25 percent based on polygraph results alone. Do the tests work? Depends how you define work. Probably the most comprehensive look at polygraph accuracy is a 2003 report from the National Academy of Sciences.

After examining 57 polygraph studies the NAS concluded: "In populations of examinees such as those represented in the polygraph research literature, untrained in countermeasures, specific-incident polygraph tests can discriminate lying from truth telling at rates well above chance, though well below perfection." Their analysis of the 30 most recent polygraph data sets showed an overall accuracy of 85 percent, and an analysis of seven field studies involving specific incidents showed a median accuracy of 89 percent. For screening purposes, though, the NAS found polygraph tests had too high a margin of error to be genuinely informative. If you made your criteria loose enough to catch most of the bad guys, you were overwhelmed with false positives; if you raised the bar enough to thin out the false positives, you missed too many bad guys. And what about those countermeasures the NAS mentioned? Yeah, that's a problem too. Because polygraph tests rely on physical reactions, if you can control or mask your reactions at key moments in the questioning, you may be able to throw off the readings enough to produce an inconclusive result.

Countermeasure techniques are surprisingly simple: they include discreet physical motions like pressing your toes against the floor or biting your tongue and mental tasks like silently counting backwards from 1,000 by sevens. The goal is to increase your baseline stress level enough to hide any revealing spikes. If polygraphs are so fallible, why use them at all? In part because testing can intimidate people into confessing, deter bad behavior, and create an impression (however misleading) of vigilance. In other words: security theater. Heeding the NAS report, in 2006 the U.S. Department of Energy stopped blanket screening of its existing and prospective employees. Polygraph tests are now saved for specified instances — say, if someone fails to report a relationship with a foreign power. Advocates of lie-detector tests foresee the day when technological advances will improve accuracy to the point where test results could be admitted as evidence. Much attention has been paid in recent years to functional magnetic resonance imaging, or fMRI. In its simplest form, fMRI lie detection works by scanning your brain to find out which areas are most active while you're being grilled; supposedly lying and truth-telling cause different areas to light up.

No doubt due to the impracticality of using multimillion-dollar machines for everyday criminal interrogations, there haven't been many large-scale studies of fMRI accuracy. But the ones I've found show an accuracy rate of 76 to 92 percent — to be generous, about the same as you get with old-fashioned equipment at a fraction of the cost. — Cecil Adams NEW: THE STRAIGHT DOPE PODCAST! No time for retro print technology? Listen to the Straight Dope while you multitask! Launch iTunes, then search for “Straight Dope” in the iTunes Store. Click on “subscribe” and Cecil’s latest installment of wisdom will be automatically delivered each week. Comment on this answer References Bellin, Jeffrey “The Significance (If Any) for the Federal Criminal Justice System of Advances in Lie Detector Technology” Temple Law Review 80 (2007): 711-742. Cumming, Alfred Polygraph Use by the Department of Energy: Issues for Congress Congressional Research Service, 2008.

Elaad, Eitan and Ben-Shakhar, Gershon “Countering Countermeasures in the Concealed Information Test Using Covert Respiration Measures” Applied Psychophysiology and Biofeedback 34 (2009):197–208. Handler, Mark et al. “Integration of Pre-Employment Polygraph Screening into the Police Selection Process” Journal of Police Criminal Psychology Published online 20 May, 2009. Iacono, William G. “Effective Policing: Understanding How Polygraph Tests Work and Are Used” Criminal Justice and Behavior 35 (2008): 1295-1308. Langleben, Daniel D. “Detection of Deception with fMRI: Are we there yet?” Legal and Criminological Psychology 13 (2008): 1–9. Mohamed, Feroze B. et al. “Brain Mapping of Deception and Truth Telling about an Ecologically Valid Situation: Functional MR Imaging and Polygraph Investigation – Initial Experience” Radiology 238.2 (2006): 679-688. National Research Council (2003).

The Polygraph and Lie Detection. Committee to Review the Scientific Evidence on the Polygraph. Division of Behavioral and Social Sciences and Education. Washington, DC: The National Academies Press. Recent Additions: 4 Ways to Cheat a Polygraph Test (Lie Detector) - wikiHow Apply Polygraph Countermeasures 1 Say only what you need to. “Yes” or “No” answers should be all you need for most of the test. Resist the temptation to explain your answers or to go into details, although the polygrapher may try to get you to do so. Be courteous and cooperative, but do not offer any more information than is absolutely necessary. 2 Don’t admit anything relevant. No matter what the lines on the chart look like, nothing is more certain or damaging than your confession. The polygrapher will most likely try to convince you that he or she can “see” a lie in your polygraph, even if there’s nothing abnormal there. Don’t fall for it. However, you want to appear honest, so don’t be afraid to make minor admissions to control questions. Just make sure you don’t admit anything in these that can invite further questioning or that may be construed as relevant.

Remember that the job of polygraphers is to extract confessions. In many ways, the whole examination is a complex ruse to trick you into confessing something. 3 Answer questions firmly, seriously, and without hesitation. This is no time to joke around or try to be crafty. You want to appear earnest, cooperative and resolute. 4 Breathe normally. Except during control questions, you should try to maintain a breathing rate of 15-30 breaths per minute. Do not breathe too deeply. 5 Alter breathing rate with control questions. The polygrapher will compare your physiological responses to control questions to your responses to relevant questions. If the deviation from normal during control questions exceeds the deviation from normal during relevant questions, you will pass. If you react more to a relevant question than to control questions, the polygrapher will perceive (rightly or wrongly) that you are lying in response to something relevant and you will likely fail the polygraph. Change your breathing pattern when a control question is asked. You can make it faster or slower, hold your breath for a couple seconds after an exhalation, or breathe more shallowly.

Do this for 5-15 seconds and return to your normal breathing pattern before the next question. 6 Answer control questions strangely. When you are asked a question that is obviously a control question, answer in a vague or odd fashion. For instance, if you're asked what year it is, you might respond with, "the year of the snake" or such an answer. Your goal is to make it difficult for the tester to get a bead on what a "normal" response is for you. 7 Think of something mentally stressful when answering a control question. If you can artificially worry yourself when answering a control question, you can modify the results of your test so that your "normal" responses appear the same as the responses that actually worry you. For instance, you might try doing mental arithmetic when a control question is asked. Count backwards by 7s in your head as quickly as possible or do some quick long division. This will help change your blood pressure and heart rate to a level that's similar to that which occurs during actual stressful situations - like answering a revealing question. Alternatively, you can mentally picture a frightening scenario, like, for instance, drowning, as this typically will also increase your heart rate and breathing. 8 Handle the post-test interview.

After you’re disconnected from the machine, the polygrapher may leave you in the room for a while and come back. The polygrapher may then claim to “know” that you are lying about something. This is a trick. Remain calm and firmly but politely repeat your denial. Don’t change or augment your answers and decline extended post-test interviewing if possible. Method Be on Your Guard 1 Remember that the polygrapher is not your friend. The polygrapher may try to convince you that he or she is on your side and will help you out if you’ll just be truthful. This is deception; don’t buy it. 2 Beware of pretest tricks. Polygraphers will frequently attempt to instill fear in the subject or convince the subject of the accuracy of the polygraph machine. The theory is that the more you fear that you may be caught, the greater your physiological reactions will be. Don’t believe the hype. The polygrapher may also try to elicit reactions from you based on fear. For example, he or she may say that you need to wash your hands so the machine can accurately read your sweat output.

A hidden camera in the bathroom may then catch the subject going into the bathroom as directed, but not washing his or her hands. Method Learn How to Recognize Question Types 1 Identify the types of questions you are being asked. There are three basic types of questions you will be asked: relevant, irrelevant and control. Irrelevant questions are those that are obvious, such as “What is your name?” or “Are the lights on in this room?” Relevant questions are the important ones, such as “Did you leak that memo to the media,” “Have you ever stolen money from an employer?” or “Have you ever sold drugs?” Control questions are those against which your reactions to relevant questions will be compared. These are usually questions to which (just about) everybody can answer “yes,” but which everybody is uncomfortable honestly answering. Examples might include, “Have you ever lied to get out of trouble?” or “Have you ever taken anything of value from an employer?” 2 Conceal your knowledge of polygraphy. The polygrapher may ask you, before the test if you’ve done any research on polygraph tests or what you know about them. Do not disclose that you’ve done extensive research.

Act as though you don’t know much about polygraph examinations, but that you do believe polygraphy to be a science and polygraphs to be reliable (or at least do not exhibit any doubt as to their reliability). The polygrapher may try to trick you by mentioning certain technical terms and acronyms such as, “Your test came back NDI.” While you will know that “NDI” means “no deception indicated,” you need to act as though you have no idea what it means. Too much knowledge of the process may make the polygrapher think you’ve got something to hide, even if you don’t. Method Prepare Well in Advance 1 Learn about polygraphs. If your career or court case depends on it, wouldn’t you do as much research as you can? Read about what they are and how the process generally works. The most important thing to know is that polygraphy is not an exact science. In fact, it is not a science at all. It was created by interrogators, not scientists, and frequently produces incorrect results. 2 Find out what the tester is looking for. A polygraph examination is administered to help find out specific information, such as whether you’re a spy or whether you’ve used drugs.

If your test is prompted by a specific incident, you probably know what the examiner is looking for. For pre-employment screening tests and the like, research the company or agency’s policies to determine what you can and cannot admit. 3 Practice countermeasures in advance. Practicing these beforehand can greatly increase the likelihood that you will “pass” the polygraph examination, but only if you do them right. Once you read about the measures, be sure to practice them well before the test so that you’re thoroughly prepared. 4 Approach your whole “polygraph day” as a test. Treat the polygraph examination as an extreme job interview. Dress conservatively and appropriately, and try to make a good impression before the test. Be sure to arrive on time and, unless it's the direst of circumstances, do not reschedule or attempt to postpone the exam. Be aware that your every move is very likely being observed from the moment you arrive at the testing location. There may be hidden cameras in the waiting room and the restrooms, and there is almost certainly a camera or two-way mirror in the polygraph room. Your polygraph examination begins long before you are hooked up to the machine and ends only when you’ve left the testing location.

Community Q&A Can I offer a bribe prior to taking a polygraph test? wikiHow Contributor To do so is illegal and it is easier to get caught bribing then cheating a polygraph. Thus, it is not a recommended course of action. Will high blood pressure affect the results of a polygraph? wikiHow Contributor Can I be found guilty if I am innocent? wikiHow Contributor A polygraph can indicate that you're lying even if you are telling the truth, especially if the test is stressing you out. Stress and lying are associated with many of the same biological responses. For this reason, polygraph results are no longer admissible as evidence in legal trials. So, if you are found guilty despite being innocent, it won't be because of a lie detector. How accurate are polygraph tests? wikiHow Contributor Unfortunate, there is no definite answer for there. It will depend on the type of polygraph, when it was made, who made it, etc. If I have a nerve disorder, would I likely fail a test? wikiHow Contributor Yes, a nerve disorder may make you fail a test even if you are telling the truth. Disclose your disorder to the test giver before the exam.

Can harming yourself, such as pinching or biting tongue, affect the polygraph test? wikiHow Contributor Yes, pain and lying cause similar results. Another way to do this is by using a thumbtack in your shoe. How do I overcome a spike in blood pressure? wikiHow Contributor Focus on what your body is doing while it's doing it. Direct your attention to slowing your breathing, and keeping it steady, thus slowing your heart rate and lowering blood pressure. Remember how mentally influenced your body is. You can even slow down your heart rate simply by paying attention to what you want it to do. By directing your attention fully to the calmness of your body, and remaining confident, you should be able to successfully cheat the polygraph. Can I pass a polygraph test by telling the truth? wikiHow Contributor Yes. That's the normal way to pass a polygraph test. Cheating is for those who don't want to tell the truth. How long does it take to get the results of the test? wikiHow Contributor The process for getting results can take minutes or hours, depending on the length of the test. If you are pregnant, can it affect the test results?

wikiHow Contributor If this question (or a similar one) is answered twice in this section, please click here to let us know. Tips Think of something that calms you down, or something you know that you never did during an accusing question. See it in your mind while answering the question. There are several subtle variations on the polygraph test. Be sure to research these thoroughly before your test to be prepared for anything they might throw at you. The easiest way to avoid failing a polygraph is to refuse one. For pre-employment screenings, this will almost certainly insure that you don’t get hired. However, it’s still a viable option, especially if you are opposed to the usage of polygraphs in general. While refusal may prevent you from getting hired, it probably will not get you fired. In the U.S., private sector employers may not terminate employment or take other such adverse actions based solely on a polygraph refusal. However, this protection usually does not cover government employees. If your polygraph is part of a criminal investigation, you have a right (at least in the U.S.) to refuse. Refusal to submit to a polygraph is generally not admissible in criminal court, and polygraph results themselves are rarely admissible.

In some states polygraph results are admissible in civil and administrative proceedings. If you are required to take a polygraph as part of your condition of probation or parole, a failed polygraph, or your polygrapher's accusation that you used of countermeasures, can be used in revocation proceedings. Warnings Perform only one heart rate/blood pressure altering countermeasure at a time or it may become too obvious. If you are accused of deception or using countermeasures, you will likely be eliminated from the job pool. If you are on parole/probation and are mandated to take a polygraph, a polygrapher's accusation that you used countermeasures may land you back in jail. Be aware that you might not be able to beat the lie detector even using these methods. Biting your tongue is highly effective, but may be detectable if you move your mouth observably. Some polygraphers make examinees wear a special set of headphones designed to measure jaw movements.

Polygraph Questions | UK Lie Detector Test UK Lie Detector Test By UK Lie Detector Test March 23, 2015 Leave a comment For many who are applying for a job in law enforcement or with certain government agencies, a required final step in the pre-employment screening process will be to pass a polygraph examination. These employers do this a final measure to make sure that all information on an application is correct, and to put you to the test at handing yourself under pressure and in an interrogation situation. Anyone who is getting a lie detector test will feel some anxiety about what to expect and how the test will work. That’s why if you have decided to pursue a job with one of these organizations, it’s best to fully understand how a polygraph works and what kind of questions they will be asking you. The Polygraph The polygraph is not some magic device that can automatically tell whether or not you have told a lie. In fact all that it does is give a detailed reading about your body while you are answering questions. As How Stuff Works explains, the polygraph can be broken down into three stages : pre-test, in-test, and post-test. All polygraph examinations will begin with an interview between the polygrapher and the examinee.

The polygrapher will ask you questions about your life, looking for basic facts about you, and then discuss the topic at hand—most likely, the job that you are applying for and the specifics of the information that you have already provided. Then, the polygrapher designs around 10 yes or no questions to ask you while you have the polygraph’s sensors attached to your body. The Questions Ehow has noted that anyone applying to be a police officer can expect certain questions, usually about your own history with the law. Have you used any illegal narcotics in the past five years? Have you ever taken part in a serious crime? Are just two examples of common questions that will come up on a police polygraph, and many other employers would most likely do the same. These would be the “relevant” questions, or the ones where your employer wants to gauge how truthful you are being. The polygrapher will also ask you “control” questions such as is your name really Bob? Do you live in this city? Asking these questions gives the polygrapher a base to study your physiological responses to telling the truth and answering simply versus a question where you might be anxious and fabricating your response.

No matter what questions you face when you go for your polygraph exam, experts agree that the best way to get through it without any issue is to stay clam, and tell the truth. This article was posted in Polygraphs . polygraph - lie detector - The Skeptic's Dictionary - Skepdic.com z polygraph ("lie detector") "I don't know anything about lie detectors other than they scare the hell out of people." --Richard Nixon "For federal agencies, the polygraph is a way to get around discrimination laws. There is virtually no appeal you can make if you are failed by a federal polygrapher. The polygraph is a license to abuse power." --Robert Todd Carroll In ancient China (circa 1000 BCE), suspected liars had to chew rice powder and spit it out. If the powder was dry the suspect was deemed a liar because, it was thought, lying increases fear and saliva flow decreases in response to fear (Vrij). During the Inquisition, suspected liars were made to chew bread and cheese. If they choked on the meal--due to a dry throat caused by fear--it might be their last (Segrave).

The idea of a physiological response to lying being detected by a simple test is an old one and seems barbaric and primitive to us. Add a few electrical wires and some technical-sounding jargon and the idea of detecting a lie by physiological response becomes "scientific." A polygraph is an instrument that simultaneously records changes in physiological processes such as heartbeat, blood pressure, respiration and electrical resistance (galvanic skin response or GSR). The polygraph is used as a lie detector by police departments, the FBI, the CIA, federal and state governments, and numerous private agencies. The underlying theory of the polygraph is that when people lie they also get measurably nervous about lying. The heartbeat increases, blood pressure goes up, breathing rhythms change, perspiration increases, etc. A baseline for these physiological characteristics is established by asking the subject questions whose answers the investigator knows. Deviation from the baseline for truthfulness is taken as sign of lying. There are three basic approaches to the polygraph test: The Control Question Test (CQT). This test compares the physiological response to relevant questions about the crime with the response to questions relating to possible prior misdeeds.

"This test is often used to determine whether certain criminal suspects should be prosecuted or classified as uninvolved in the crime" (American Psychological Association). The Directed Lie Test (DLT). This test tries to detect lying by comparing physiological responses when the subject is told to deliberately lie to responses when they tell the truth. The Guilty Knowledge Test (GKT). This test compares physiological responses to multiple-choice type questions about the crime, one choice of which contains information only the crime investigators and the criminal would know about. Psychologists do not think either the CQT or the DLT is scientifically sound, but a majority surveyed by the American Psychological Association think that the Guilty Knowledge Test is based on sound scientific theory and consider it "a promising forensic tool." However, they "would not advocate its admissibility [in court] in the absence of additional research with real-life criminal cases." One major problem with this test is that it has no controls. Also, unless the investigators have several pieces of insider information to use in their questioning, they run the risk of making a hasty conclusion based on just one or two "deviant" responses. There may be many reasons why a subject would select the "insider" choice to a question.

Furthermore, not responding differently to the "insider" choices for several questions should not be taken as proof the subject is innocent. He or she may be a sociopath, a psychopath, or simply a good liar. Is there any evidence that the polygraph is really able to detect lies? The machine measures changes in blood pressure, pulse, and respiration rate. When a person lies it is assumed that these physiological changes occur in such a way that a trained expert can detect whether the person is lying. Is there a scientific formula or law which establishes a regular correlation between such physiological changes and lying? No. Is there any scientific evidence that polygraph experts can detect lies using their machine at a significantly better rate than non-experts using other methods? No. There are no machines and no experts that can detect with a high degree of accuracy when people, selected randomly, are lying and when they are telling the truth. Some people, such as Senator Orrin Hatch, don't trust the polygraph machine, even if used by an expert like Paul Minor who trained FBI agents in their use. Anita Hill passed a polygraph test administered by Minor who declared she was telling the truth about Clarence Thomas.

Hatch declared that someone with a delusional disorder could pass the test if the liar really thought she was telling the truth. Hatch may be right, but the ability of sociopaths and the deluded to pass a polygraph test is not the reason such machines cannot accurately detect lies with accuracy any greater than other methods of lie detection. The reason the polygraph is not a lie detector is that what it measures--changes in heartbeat, blood pressure, and respiration--can be caused by many things. Nervousness, anger, sadness, embarrassment, and fear can all be causal factors in altering one's heart rate, blood pressure, or respiration rate. Having to go to the bathroom can also be causative. There are also a number of medical conditions such as colds, headaches, constipation, or neurological and muscular problems which can cause the physiological changes measured by the polygraph. The claim that an expert can tell when the changes are due to a lie and when they are due to other factors has never been proven. Even if the device measures nervousness, one cannot be sure that the cause of the nervousness is fear of being caught in a lie.

Some people may fear that the machine will indicate they are lying when they are telling the truth and that they will be falsely accused of lying. Furthermore, even the most ardent advocate of the polygraph must admit that liars can sometimes pass their tests. One need only remember the spy Aldrich Ames , who passed the polygraph test several times while with the CIA. This lesson was lost on the FBI, however, who started requiring polygraph tests of its employees after spy Robert Hanssen was caught. Heretofore, the FBI had only used the polygraph on suspected criminals. Apparently, the FBI thinks that they could have prevented Hanssen's betrayal if only he had been made to take the polygraph. In California and many other states, the results of polygraph tests are inadmissible as evidence in a court of law. This may because polygraph tests are known to be unreliable, or it may be because what little benefit may be derived from using the polygraph is far outweighed by the potential for significant abuse by the police. The test can easily be used to invade a person's privacy or to issue a high-tech browbeating of suspects.

Skeptics consider evidence from polygraphs no more reliable than testimony evoked under hypnosis , which is also not allowed in a court of law in California and many other states. Also, in 1998, the U.S. Supreme Court argued that Military Rule of Evidence 707, which makes polygraph evidence inadmissible in court-martial proceedings, does not unconstitutionally abridge the right of accused members of the military to present a defense (United States, Petitioner v. Edward G. Scheffer). The American Civil Liberties Union strongly supported the passage of the Employee Polygraph Protection Act of 1988 (EPPA) which outlaws the use of the polygraph "for the purpose of rendering a diagnostic opinion regarding the honesty or dishonesty of an individual." The EPPA doesn't outlaw the polygraph across the board, however. Federal, state and local governments can still use the polygraph. The federal government can give polygraph tests to government contractors involved in national security projects. In the private sector, security and pharmaceutical firms can still use the polygraph on current or prospective employees.

Furthermore, any employer can administer polygraph tests ...in connection with an ongoing investigation of an economic loss or injury to his/her business on these conditions: The employee under suspicion must have had access to the property, and the employer must state in writing the basis for a reasonable suspicion that the employee was guilty (ACLU). The ACLU supported the EPPA not only because of the lack of evidence for the accuracy of the polygraph, but because of abuses related with its administration, including, but not limited to, the invasion of privacy. For example, in order to establish "normal" physiological reactions of the person being tested, "lie detector" examiners ask questions that purposely embarrass, frighten and humiliate workers. An ACLU lawsuit in l987 revealed that state employees in North Carolina were routinely asked to answer such questions as "When was the last time you unintentionally exposed yourself after drinking?" and "Who was the last child that got you sexy?" Polygraphs have been used by unscrupulous employers to harass union organizers and whistle-blowers, to coerce employees into "confessing" infractions they did not commit, and to falsely implicate fellow employees (ACLU).

Why would so many government and law enforcement agencies, and so many private sector employers, want to use the polygraph if the scientific community is not generally convinced of their validity? Is it just wishful thinking ? Do the users of the polygraph want to believe there is a quick and dirty test to determine who's lying and who's not, so they blind themselves to the lack of evidence? Perhaps, but there are other factors as well, such as the esoteric technology factor. The polygraph machine looks like a sophisticated, space- age device of modern technology. It can be administered correctly only by experts trained in its arcane ways. Non-experts are at the mercy of the high-tech, specially trained wizards who alone can deliver the prize: a decision as to who is lying and who is not. Another reason for the polygraph's popularity is the pragmatic fallacy factor: it works! Case after case can be used to exemplify that the polygraph works. There are the cases of those who failed the test and whose lying was corroborated by other evidence. There are the cases of those who, seeing they are failing the test, suddenly confess.

What is the evidence that the rate of correct identification of lying corroborated by extrinsic evidence is greater than the rate of identification of lying by non-technological means? There isn't any. The proofs are anecdotal or based on fallacious reasoning such as thinking that a correlation proves a causal connection. On the other hand, it is possible that one of the main reasons so many government, law enforcement and private sector employers want to use polygraphs is that they think the test will frighten away liars and cheats who are seeking jobs, or it will frighten confessions out of those accused of wrongdoing. In other words, the users of the machine don't really believe it can detect lies, but they know that the people they administer it to think the machine can catch them in a lie. So, the result is the same as if the test really worked: they don't hire the liar/cheat and they catch the dishonest employee. See also e-meter and ideomotor effect .

Michael Shermer Tests the Polygraph further reading How do Lie Detectors Work and are They Accurate - Denver Criminal Attorney Specializing in Criminal Defense for Denver - Colorado Criminal Lawyer How do Lie Detectors Work and are They Accurate Justice by Machine: Living with Lie Detector Tests by Steve Elias A former public defender recounts his first experience with a lie detector test and argues for their place in American courtrooms. I vividly remember my first lie detector test. It wasn’t I who was being tested but rather a client charged with rape. I was relatively new to the criminal defense business, having recently been hired by the State of Vermont as Public Defender of the Northeast Kingdom (as the three Northeastern most Vermont counties were called). Before the test began, the test operator took me aside to explain how it works. “It’s real simple,” he said. “First I explain the basic theory of the test to the subject: that lying causes anxiety that shows up on my graphs. Then I explain that the test is called a polygraph because I graphically track three of their unconscious physiological responses at the same time.

Then I explain that they can’t get away with lying to me since only someone trained as a yogi can simultaneously control all three physiological responses (breath, heart rate and galvanic skin response). Then I wire them up to these graphs and tell them to pick a number between one and ten. I tell them to answer no each time I guess a number, even if I guess the right number. When they answer no to the right number, it always causes a spike in the graphs. I stop the procedure at that point, tell them they lied and show them the graphs. Now that they’re convinced that my graphs can read their mind, their responses go haywire when they lie in the course of my actual questioning. The fact is, very few of the people I test bother to lie after this introduction. I get more confessions than the police ever could by a mere interrogation.” Sure enough, my client who had up to that point steadfastly proclaimed his innocence to me, as well as everyone else concerned with his case, confessed his guilt rather than lie to someone whom he believed knew when he was lying. I was convinced. And because I was a believer, I tended to discourage my clients from submitting to lie detector tests.

The truth was that I could frequently do a much better job for my clients if I could maintain a personal belief in their innocence. In some cases, however, the prosecution made offers of leniency contingent upon my client being willing to go on the box (as the test is colloquially called). And so, in the course of my three-year public defender stint, about a half dozen clients voluntarily submitted to a lie detector test in hopes of a better deal. And, with just one exception, they either confessed during the test or confided their guilt to me after the test indicated their responses to be deceptive. I remained a believer. What about the exception? The results were inconclusive; the operator said he suspected valium. Since my I knew that my client had a long-standing valium problem, I thought this was a pretty good call. In any event, when his case went to trial, the jury, as ultimate lie detector, didn’t believe him and came in with a guilty verdict. Are Lie Detectors Telling the Truth? You may wonder how, in the absence of a confession, a polygraph operator can confidently determine whether a person is lying.

Don’t most people — even innocent ones — get stressed when being asked questions that might land them in big trouble? Yes, but the polygraph operator has techniques to overcome this problem. Before getting to the nitty-gritty of the issue (“Did you do it? Were you There? Do you have any personal knowledge of what happened?”) the operator first asks a series of questions, some of which are emotionally neutral and some of which are calculated to cause emotional discomfort based on the test subject’s personal circumstances. The subject’s physiological responses to these questions are meticulously calibrated. Then, when the operator gets around to the core questions, the responses to those questions can be measured and compared to the responses produced by the neutral and control questions. It’s true, a lot of devils can live in the space of relative anxiety measurements, but numerous independent tests have indicated an accuracy rate in the 80-90% range. So if these tests are so accurate, why aren’t they required in every situation where truth is at issue? Why spend billions of dollars on jury trials and independent prosecutors when we could just “wire up” the key witnesses and get at the truth with no fuss and no muss? The U.S.

Supreme Court recently decided a case that deals with this very subject. In United States v. Scheffer, 000 U.S. 96-1133 (1998) the Supreme Court upheld a military court evidence rule (Rule 707) that prohibits the use of lie detector results in military trials. In this case, Scheffer, a military investigator, took a routine urine test. The test came back positive for amphetamines. Scheffer then asked for and was given a polygraph test which showed he had no knowledge of amphetamine use. At his trial on drug use charges based on the urine test, Scheffer tried to introduce evidence of his favorable lie detector results. The court refused to admit this evidence on the basis of military evidence Rule 707.

Scheffer appealed on the ground that he should have been able to introduce the test results as part of his constitutional right “to prepare a defense.” The Supreme Court upheld Rule 707 for these reasons: there is too much controversy about the reliability of lie detector test results lie detector tests might undercut the role of the jury in assessing witness credibility, and lie detector tests create the possibility of vexing side issues about the reliability of the test. To Err Can Be Mechanical Without question, lie detector tests are controversial. Putting aside their utility as interrogation devices, the validity of their results depends on a lot of things being done right — the right control questions, the right neutral questions, the right core questions, the right interpretation of the graphs, the right setting for the questioning, and so on. And not all scientific evaluations have concluded that they are accurate even when everything is done right. Many evaluations have concluded that polygraph results are more likely to be valid if they show innocence than if they show guilt. This is because there are lots of situations where a defendant may have a guilty mind (and thus show up as deceptive on the polygraph results) but not in fact be guilty. It’s the same as flight.

When a defendant runs away from the police or the scene of the crime, a jury is entitled to infer a guilty mind. But flight doesn’t necessary equal guilt. Innocence, on the other hand, is much more unequivocal. But even here, some people are so divorced from morality or a guilty conscience that they may test honest — because they are really good liars or have convinced themselves of a truth that isn’t the truth at all. Last but not least, it may be possible to throw the results through other methods, such as yogic or biofeedback training, the “nail in the shoe” trick (putting a sharp nail in your shoe to cause yourself pain during the questions to skew the polygraph results), or using a legal or illegal drug to calibrate one’s emotions. Simply put, there is no way to turn a lie detector test into a slam dunk. For this reason, most courts will not admit polygraph results unless both sides to the case agree. To those who believe in polygraph tests, the answer to these reliability issues is, so what? Lots of other types of evidence also have problems. Consider urine tests, for example.

There are lots of things that can go wrong with a urine test, including laboratory contamination, false positives and passive smoke. ( In Scheffer’s case, however, a urine test was admitted against him, but the polygraph test was not admissible as a defense. Of course other types of evidence which are notoriously unreliable are also routinely admitted into military (and most other) trials, including eye witness testimony (especially cross-race eyewitness testimony), evidence of demeanor (he “looked” guilty) and, as mentioned, evidence of a guilty mind such as flight. Man, Machine or Both The concern that the polygraph may supplant the jury as the judge of witness credibility raises some interesting issues. It is founded on a fear that the jury will abandon its human-based assessment of a witness’s credibility and instead rubber-stamp the machine’s version of the truth. To be sure, if we were wise, we would be very careful about how much of our important affairs we turn over to machines. Unfortunately, we’ve already pretty much given away the store on this one. Drug tests, DNA matching, child support calculations, computer-generated profiles and credit scoring are just some of the types of machine-based information we use for important commercial, employment and judicial transactions.

If we can trust juries to remain independent in the face of the junk science that is already routinely admitted into evidence — notably, psychological profiles and assessments of mental states — then perhaps we should also rely on juries to remain independent in the face of a test that, independent studies indicate, is likely to be right at least 80-85% of the time. Other Articles of Interest: USATODAY.com - Lie detectors are likely lying themselves Text Lie detectors are likely lying themselves I learn a lot watching television. That is, I learn a lot by watching television and thinking, "That can't be right!" then doing the research to find the full story. Television butchers technology. It has to. There's no time in your average crime drama, say, to go into the details of tracking a cell phone or running someone's DNA; what takes seconds on TV often takes hours in the real world. (I understand that they've only got 42 minutes to work with, so I don't sweat the time thing.) It's when they deviate from reality so much that my goat gets got. For example, I gather I'm one of the few Americans who doesn't watch 24.

I stopped after the first episode of the first season, when Jack Bauer (that's Kiefer Sutherland to you and me) demanded of his geek-in-residence, "I need every Internet password associated with this phone number!" And he got it. It just doesn't work like that. One thing occasionally comes up on TV that I wasn't sure which category it belonged to—"accurate but glossed over" or "totally wrong." That was polygraphs. Lie detectors. On TV, the suspect is hooked up to a machine that traces a dozen or so lines on scrolling graph paper. When she tells the truth, the lines barely move. When she lies, the lines vibrate like a seismograph in an 8.0 earthquake. My guess was that in the real world a lie isn't quite so obvious, but that a trained examiner would be able to spot it right away. Boy was I wrong. It turns out that polygraphy is not only an incredibly inexact science, but that reading the results of a lie detector is almost entirely subjective. In short, lie detectors don't work. But people's lives have been ruined by them.

The problem isn't that the machines don't record something—they do: heart rate, respiration, sweat-gland activity, and so on. But what the changes in those numbers mean is entirely up to interpretation. Obviously there are two sides to this. On the one you have the American Polygraph Association (APA) and some law enforcement agencies. Neither of these are what you would call objective. The APA's existence depends on people accepting that lie detectors work, and as we've seen all too often, police and district attorneys are happy to have something that appears to provide evidence that can convict someone. (Lie detector tests are rarely allowed as evidence against someone in court — that should tell you something — but "failing" a test can sway public opinion, and jury members aren't hermits.) On the other side you have, well, dozens of groups and organizations with names like AntiPolygraph.org and StopPolygraph.com . If you're like me, you might at first blush think these are fringe groups with their own (hidden) agenda, and that they aren't about to provide unbiased information. After all, there's always a conspiracy theorist to be found.

Except that also on the anti-polygraph side I found the American Medical Association, the American Psychological Association, and 60 Minutes. They all found essentially the same thing: Lie detectors show what the examiners want them to show. In 1986, 60 Minutes demonstrated this rather dramatically. Using Popular Photography magazine as a front, the producers hired several polygraphers to help find someone who had, they were told, stolen hundreds of dollars of photographic equipment. (No such theft had taken place.) Each examiner was told that a different one of the 'suspects' was probably the guilty party. Lo and behold, each polygrapher fingered the suspect they were told ahead of time was probably guilty. Oops. An American Medical Association expert testified before Congress that "the [lie detector] cannot detect lies much better than a coin toss." Further, an article published in the Journal of the American Medical Association by the AMA's Council on Scientific Affairs said in part, "Though the polygraph can recognize guilty suspects with an accuracy that is better than chance, error rates of significant size are possible." Ouch.

A 1997 survey by the American Psychological Association found that psychologists feel that "The use of the polygraph (lie detector test) is not nearly as valid as some say and can easily be beaten and should never be admitted into evidence in courts of law." Eek. In a briefing paper from 1996, the ACLU wrote : "Despite the claims of 'lie detector' examiners, there is no machine that can detect lies with any degree of accuracy. The 'lie detector' does not measure truth-telling; it measures changes in blood pressure, breath rate and perspiration rate, but those physiological changes can be triggered by a wide range of emotions such as anger, sadness, embarrassment and fear." THREE KINDS OF POLYGRAPH TESTS Only on television do polygraphers simply ask "Did you kill your wife?". In the real world the tests are complex; different tests ask different kinds of questions. The most common form, and the one that no one of consequence seems to think is valid, is called the Control Question Test (CQT).

It compares a suspect's reaction to relevant questions ("Did you strangle your boss?") with questions relating to possible prior, um, misdeeds ("Have you ever stolen anything from someplace you worked?"). Another kind is the Directed Lie Test (DLT), in which a suspect is told to deliberately lie before being asked the relevant question in order to see the differences in reaction. This is also of, shall we say, questionable validity. The only kind of polygraph test that shows any kind of accuracy is the Guilty Knowledge Test (GKT). Rather than ask "Did you shoot your husband," the GKT attempts to determine whether the suspect knows something that only the guilty party would know (e.g., "Did you know that the knife was thrown out the kitchen window?"). Unfortunately, it's the least valid of these tests, the CQT, that is most often used. (In the interests of accuracy, I should point out that these comments are regarding the most popular lie detector test, called the Control Question Test. See the sidebar.) What does the APA have to say about this? Obviously they have a strong, convincing argument demonstrating that polygraphs are incredibly accurate. Or not.

According to its Web site , the organization has collected the results from 80 research projects published since 1980. Of those, 12 showed polygraphs to have 98% average accuracy, 11 showed 92% accuracy, 41 showed 80% accuracy, and 16 showed 81% accuracy. In other words, of these 80 studies the APA itself mentions well more than half indicate the tests are wrong 19 or 20% of the time! How would you like to be the one out of five who loses his job because of an inaccurate polygraph test? One out of five — most of us would call that unconscionable. (And job losses due to polygraph-like tests are nothing new. In the 1950s and '60s, several organizations in Canada — including the military, police, and civil service — tested applicants by measuring their perspiration, pupils, and pulse rate when shown pornographic images. Although subjects were told these tests were to measure stress, this cousin of the polygraph was actually designed to 'detect' homosexuality.

Nicknamed the Fruit Machine, it cost a lot of people their jobs before it was finally eliminated.) The APA goes on to say, "While the polygraph technique is not infallible, research clearly indicates that when administered by a competent examiner, the polygraph test is one of the most accurate means available to determine truth and deception." Switching to my Language Guy hat, this is a sentence you can't argue with. Considering that there is no real way to accurately determine truth or deception, saying that the polygraph is "one of the most accurate" ways is like saying "Reading tea leaves is one of the most accurate ways of divining the future." It's easy to compare yourself to zero. People are more willing to believe that a polygraph is actually detecting lies because, unlike tea leaves, there's science involved—there are electrodes and graphs and machines. Technology just seems trustworthy. Unfortunately it's not, because lie detection isn't based on the technology itself so much as on the interpretation of what the tech says. And human interpretation is always subjective, as 60 Minutes proved.

Here's my advice: If you're ever asked to take a polygraph test, say "No way." If you have to — if it's a job requirement — relax and tell the truth. It won't make much of a difference. Andrew Kantor is a technology writer, pundit, and know-it-all living in Columbus, Ohio; he's also a former editor for PC Magazine and Internet World. Read more of his work at kantor.com . His column appears Fridays at USATODAY.com.

Question: What is the correct name for the lie detector?
Answer: Polygraph