The first question I would ask Obama would be if he is determined to whatever it takes to bring the troops home within a year of taking office?

Thus might be of little use for Politicians.

http://skepdic.com/polygrap.html

polygraph ("lie detector")

"I don't know anything about lie detectors other than they scare the hell out of people." --Richard Nixon

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:

1. 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).
2. 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.
3. 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, breath rate, 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.