What are lie detectors?
Lie detectors have long been a point of fascination for both law enforcement and the general public. However, they are also often misunderstood, which can lead to them being misused. The more information you have about lie detectors- how they work and their purpose – the easier it is to determine if and when these tests are appropriate for a given circumstance. It sounds fancy and high tech, but the reality is that lie detection is really just another word for a polygraph. Officially, a polygraph measures several things in order to determine if someone is lying or not: blood pressure, pulse, respiration, and skin conductivity. It gauges these four indicators throughout the course of a typical interview process – often called a polygraph test – which can take up to two hours.
The polygraph is generally not a single test in order to detect lies. Instead, an examiner will hook the subject up to the machine, ask them a series of questions, take note of their physiological responses, and use these responses to determine if they were telling the truth at the time or not . While there are different types of polygraphs and testers may label their tools differently, the basic function and process is essentially the same. A polygraph test starts with an interview and a line-by-line analysis of the questions. The tester then attaches the sensors to the subject and has them listen to the questions while they are answered. While there are several different policies, sensors and machines available on the market, most fall into a few standard kinds: To most people, polygraph tests are synonymous with criminal investigations, but they can serve a vital role in many situations. One common example is for employment drug screening, which most states do not prohibit. There are also a variety of other uses of these tests: Even legally obtained polygraph evidence is not always allowed in the courtroom; courts often weigh the probative value against the prejudicial effect before allowing the admission of such evidence.
The legal limitations of lie detectors in court
The legal status of lie detectors in courtrooms is complicated and varies widely across countries and states. In federal courts in the U.S., the current consensus is that the results from lie-detector tests are inadmissible as evidence. While there have been notable cases in the past where the results were accepted, such as when the Government of the Virgin Islands v. Davis and Strategic Systems, Inc. v. NSS Labs both saw polygraph results being introduced in federal civil actions, those decisions were based less on the reliability of the results, and more on the specifics of the situations. In both, the results were submitted voluntarily and agreed upon beforehand by all parties involved. A lack of "police coercion" made the inclusion of the results appropriate under these circumstances. In more recent cases such as United States v. Montoya, the evidence was excluded due to the lack of established reliability in the testing method.
The same standards cannot be said to apply at the state level. In Maryland, for instance, The Maryland Appellate Court ruled in 2003 that the results of a polygraph test could be used in official evidence if both parties agreed to it. The outcome in this case was influenced by a 1997 Maryland law change which allowed polygraph results to be used in court under certain circumstances.
Polygraph testing, along with multiple-choice polygraph testing, is still currently banned in many states throughout America and England, mainly due to the fact that there has yet to be a consensus on the reliability of the technique. On the international level, at least 15 countries have explicitly prohibited the use of lie detectors in court, including Belgium, France, Italy, Malaysia, and numerous others.
Supporting opinions on legality of lie detector results in court
Proponents both in the legal and scientific communities have long argued that polygraph examinations should be admissible at trial on the basis of their proven reliability. They note that polygraph technique is no more complex than taking a blood pressure reading and can provide law enforcement with a no cost, fast, and generally accurate means to eliminate or find potential suspects. For civil disputes, polygraphs can be used to settle personal injury claims, marital disputes, and inheritance claims.
Some argue that the integrity of the polygraph test is not harmed by the results being made public because the test results may have no effect on the outcome of a civil trial, even if admitted into evidence. Further, in these cases, the jury will have the benefit of hearing polygraph testimony from both parties and will be able to determine the accuracy of the test. This requirement is not in place in a criminal trial where only the results of the defendant’s polygraph will be available.
Though many scientists accept polygraph results as being accurate and reliable, there are many others that do not. The National Academy of Sciences, Drug Enforcement Administration, FBI, and several national and local law enforcement organizations support research on, but do not endorse, the use of polygraph in a forensic setting. Several large scale studies conducted by the National Institute of Justice found that studies consistent with the "back probing" technique (asking questions based on truthful facts) were accurate, but that most polygraphers do not use such a technique on a regular basis.
Lawyers are banned from offering polygraph results in court under the Federal Employee Polygraph Protection Act (29 U.S. Code § 2001). On a federal level, the law bars the government from using polygraph tests to screen federal government employees for employment. Some states (New York and Oklahoma) have passed laws that prohibit the use of polygraph evidence in legal proceeding as arguing a study out of California indicated that assuming a defendant was honest, the test doubled the chances of convicting an innocent person. Some point out that there are multiple other techniques available, such as fingerprints, blood, and hair testing that are not accepted by all courts and which we cannot control our body in order to appear innocent.
Case law: admissibility of lie detectors
The Polygraph Protection Act of 1988 (29 U.S.C., Sec. 2001-2005) allows employers to use lie detector tests for job applicants or employees only in very limited circumstances, such as the security of national defense or sensitive government work.
Separately, the Employee Polygraph Protection Act (15 U.S.C., Sec. 2001-2081) imposes restrictions on the use of lie detectors in the workplace by private business and industry. Employers are not allowed to require, request, or suggest that any employee or job applicant take a lie detector test.
In the cases discussed below, the courts acknowledged the potential unreliability of polygraph tests:
United States v. The City of Chicago, Illinois, 1993 Trial Decision: The U.S. Department of Labor sued the Chicago Police Department (CPD) for failing to hire women as police officers. The case went to trial and the plaintiff requested polygraph testing of police applicants as part of the class-incorporation process, claiming polygraph tests would help identify systematically disqualified women from the original police pool . The court refused to allow polygraph examination with regard to police applicants, stating: "the accuracy and reliability of the polygraph is not sufficient for such a person highly authoritative decision as deciding whether an individual is or is not suitable for employment as a police officer, a position of considerable responsibility."
Maree v. Land Air Express of Ne. Pac., 2014 U.S. Dist. LEXIS 56482 (E.D. Pa. Apr. 21, 2014): A female cell manager at Land Air Express of Northeast Pacific and its president were charged with false imprisonment and other offenses after several delivery personnel entered a new employee’s home without her consent. The cellular manager thought it was a fire drill, and that the new employee was "playing a trick" on her by calling her on the intercom. The manager was convicted and filed a motion for a new trial citing juror misconduct. She wanted to impeach juror testimony through the use of polygraph evidence. The U.S. District Court held that the polygraph evidence was inadmissible under the federal common law, Federal Rules of Evidence and Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579 (1993).
Alternative methods to lie detectors for the purposes of legal investigations
While some alternatives do exist, they are not always as accurate and reliable as a polygraph. Courts and police often use brain scans, voice stress analysis, and even statement analysis instead of lie detectors.
Brain Scans. Brain scans, such as fMRI and PET scans, are gaining ground as a replacement for polygraphs. They’re used to measure changes in blood flow and other activity in the brain that correspond to thoughts. To use this method, subjects must be shown a series of pictures and their responses to the images are recorded in the brain scan. Then a series of questions is asked. The brain scan shows how the brain was reacting during your response. If something in your brain scan did not match your self-reported truthfulness, that would be seen as deception.
The advantage of brain scans is that neuroscience is a burgeoning area of research. Brain scans are becoming more accurate and widespread, with fMRI scans actually being incorporated into criminal investigations by some law enforcement agencies. But, they’re not as widely used as polygraphs.
Voice Stress Analysis. Voice stress analysis is another method used in place of polygraphs. By placing a small microphone up close to the subject, and asking a series of questions, investigators claim to be able to record changes in a subject’s voice. Some voice stress analysis experts argue that there’s a change in your voice when you lie, even if it’s too small to pick up on a recording without intense amplification. In essence, the audio recording is taken home, and magnified, then replayed for the investigators. Proponents of this method claim a 98 percent accuracy rate. Critics, however, doubt the effectiveness of this method, stating that it has little scientific merit and that the subject’s motivations can play a large role in their accuracy. The Baglien case 1993 of the Washington Court of Appeals, Division One found no research supporting voice stress analysis (VSA) and ruled that it was inadmissible as evidence.
Statement Analysis. Statement analysis is the final alternative to polygraphs. This method is based on an assumption that micro-expressions in verbalized statements reveal a subject’s inner thoughts and feelings. For example, a person might say, "I found the money," instead of "I took the money." Intentional wording choices indicate cognitive dissonance, or that something is amiss. Statement analysis is not often used by police departments, but only by trained individuals. It is fairly uncommon.
Future use of lie detectors in the court of law
As technology continues to advance at a rapid pace, it’s not out of the realm of possibility that lie detectors will evolve to be even more effective at detecting deception. Ongoing research into brain activity, for example, may lead researchers to develop new methods of interrogation that could reveal far more than a standard polygraph test can. This could shift perceptions around lie detectors and their reliability.
At the same time, lawmakers may alter legal standards and regulations surrounding the use of lie detectors to better align them with the evolution of brain science and technology. For example , could it become a requirement for a defendant to submit to a lie detector test upon arrest? That would certainly impact the frequency with which lie detectors are used within the judiciary.
Perhaps lie detectors will one day be exclusively administered by impartial third parties with no vested interest in the case at hand. This would help ensure the tests are fully objective, regardless of who requests them or how they’re interpreted.
The future usefulness of lie detectors in the judicial system could be much brighter, depending on advances in scientific understanding and the way in which science is implemented in the legal system. There’s still much to learn about the human brain and its role in deception, which provides insight into a person’s character and state of mind. As long as lie detectors are subject to rigorous testing and verification, they have the potential to be a valuable tool for the justice system.