Should Polygraphs be used in Court Rooms as Admissible Evidence?

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Polygraph, a practice often deemed pseudoscience by scientists, has faced substantial criticism. Until 1998, state and county courts were able to accept polygraph evidence as valid for conviction. Nonetheless, the reliability of these tests remains unproven, raising concerns regarding their susceptibility to both inaccuracies and manipulation. Consequently, it is advised against employing polygraphs prior to or during trials. Within the realm of mental health, numerous scientists either abstain from relying on polygraphs or actively oppose their utilization in legal proceedings.

The polygraph, also known as a “lie detector,” has a contentious history in U.S. legal proceedings. Invented in the late 1800s, it currently serves as an electromechanical device that is attached to individuals during interrogations. By tracking involuntary bodily changes, the polygraph claims to offer valuable insights into the truthfulness of statements. Nevertheless, this essay argues against allowing polygraph tests as acceptable evidence in court.

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Is it acceptable to allow polygraphs as admissible evidence in courtrooms? Polygraph, also known as a lie detector test, is an instrument that records and measures multiple physiological indicators such as blood pressure, pulse rate, respiration, breathing patterns/rates, and skin conductivity. During the examination process, individuals are asked various questions. The general belief is that deceptive responses will trigger distinct physiological reactions that can be distinguished from those associated with truthful answers.

Polygraphs have been employed in both judicial and non-judicial contexts, but doubts persist regarding their credibility as evidence. The Supreme Court and other courts do not recognize them as valid. Additionally, psychology questions the accuracy of polygraph tests due to their susceptibility to manipulation, which may result in misinterpretation or erroneous outcomes. Critics argue that relying on such unreliable methods would be unfair when determining an individual’s freedom or life.

The United States maintains that its justice system is fair, but it would be unjust to deem a polygraph test as credible evidence in a trial. Accusations of crimes or legal charges have a profound impact on individuals’ lives. Hence, any trustable evidence should possess substantial or compelling clarity. The justice system adheres to specific proof standards that must be met, which the polygraph test fails to satisfy. Admissible evidence must be relevant.

Having relevant evidence is essential for determining the outcome of a case, as it can either strengthen or weaken the probability of a particular fact being true. In relation to polygraph tests, commonly referred to as “lie-detectors,” they have been considered insignificant evidence. The Supreme Court case United States v. Scheffer was significant because it set a precedent for the Court’s initial ruling on the admissibility of polygraph evidence in military courts. The primary concern was whether excluding this form of evidence violated the defendants’ Sixth Amendment right to present their defense.

In United States v. Scheffer, a former U.S. airman faced court-martial for various offenses: using methamphetamines, passing bad checks, and going AWOL. The U.S. Court of Appeals for the Armed Forces declared that the military’s ban on polygraphs was unconstitutional despite Scheffer passing a polygraph test on illegal drug use.

The court believed that Scheffer should have been given an opportunity to demonstrate the reliability of the polygraph results similar to other forms of evidence. However, the Supreme Court overturned this ruling and determined that excluding the polygraph evidence did not significantly disadvantage Scheffer.

Thomas, Chief Justice William H. Rehnquist, Antonin Scalia, and David H. Souter sought to maintain the prohibition of polygraph evidence in court by states to discourage its use. Thomas argues that polygraph evidence may undermine the jury’s credibility determination, justifying the ban on polygraphs in court and urging states not to allow their use due to the high probability of unreliable test results.

Polygraph tests are frequently criticized for their vulnerability to manipulation and external influences, which can affect their accuracy. In the case of US v. Scheffer, the Supreme Court determined that Military Rule of Evidence 707 did not infringe upon the rights of accused military members to present a defense. Although defendants have the right to present pertinent evidence, this privilege can be reasonably limited in order to safeguard other lawful interests during criminal proceedings.

State and federal authorities have considerable leeway under the Constitution to create regulations that prohibit the use of evidence. However, these regulations must not be arbitrary or excessive in relation to their intended objectives in order to safeguard an accuser’s right to present a defense. The Court determined in this specific instance that excluding evidence would only be unconstitutional if it violated a significant interest of the defendant. The evidentiary regulation being discussed here is Rule 707, which seeks to guarantee the admission of trustworthy evidence.

In this case, the court had to consider whether the defendant’s inability to use polygraph results as evidence of innocence and their reliability constitutes impairment. According to previous rulings by this Court, Rule 707 did not raise a constitutional concern because it did not involve a significant enough interest for the accused. The Court of Appeals relied mainly on three cases: Rock v. Arkansas, 483 U. S. 44, 55; Washington v. Texas, 388 U. S. 14, 23; and Chambers v. Mississippi, 410 U.S.84,302-303 – none of which supported the right to introduce polygraph evidence in certain situations. However, in US v.Scheffer, the exclusion of unconstitutional evidence mentioned in those cases significantly weakened important aspects of the accuser’s defense presented by them.The court members were well informed about all pertinent details regarding the charged offense from respondent’s point of view.Rule707 didn’tprevent him from presenting any factual proof but restricted his ability to provide expert opinion testimony that would have strengthened his own credibility.

Polygraph Use 4 In contrast to the rule at issue in Rock, Rule 707 did not forbid respondent from giving testimony to defend himself; he willingly utilized his opportunity to present his account of the events during the trial. The accuracy and true results of the polygraph test are not legally relevant. The legal concern regarding the polygraph test arises when either the defense or the prosecution seeks to introduce it as evidence to establish or discredit guilt or credibility. This is when the polygraph test becomes a matter of admissibility as evidence.

The accuracy and manipulability of lie detector tests make them a concern in the mental health world. Frye v. United States had a significant impact on polygraph testing. In the past, these tests were not accepted as evidence in most courts. However, as lie detection became more respected in the scientific community during the 1970s and 1980s, some courts started allowing this evidence in specific situations and with certain limitations in both criminal and civil trials.

Although the Frye v. US ruling was widely accepted by federal and state courts in the early 1970s, numerous state courts continue to reject all types of polygraph evidence. The case centered around James Alphonzo Frye’s appeal against his second degree murder conviction. After initially confessing and later retracting his admission, he faced prosecution from the federal government and ultimately received a guilty verdict from a jury in a Washington, D.C. trial court.

During the trial, Frye was prohibited from introducing evidence regarding his truthfulness through a “systolic blood pressure deception test,” an early form of the modern lie detector or polygraph test. Additionally, the court denied Frye’s plea to have an expert witness testify about this deception test. Frye’s appeal centered exclusively on the trial court’s exclusion of the deception test. The Court of Appeals of the District of Columbia, consisting of three judges, unanimously supported the United States in a concise opinion that became widely known among federal appeals court decisions.

Frye established the criteria for admitting scientific evidence, which courts relied on for seventy years before the Federal Rules of Evidence were introduced. Under Frye’s standard, evidence could be deemed admissible if it had extensive acceptance in the scientific community. However, as science progressed and expanded, this criterion became increasingly difficult for courts to manage. In 1993, in the landmark case Daubert v. Merrell Dow Pharmaceuticals, Inc., the Supreme Court declared that Rule 702 of the Federal Rules of Evidence should govern the admission of expert testimony.

The Court’s ruling declares that expert testimony does not necessitate general acceptance in the scientific community, but rather demands a reliable scientific basis and pertinence. This ruling supersedes Frye and does not automatically render polygraphs admissible as they are not explicitly mentioned in this regulation. Furthermore, polygraph tests serve both investigative objectives and post-evaluation of offenders.

The trained polygraphists use the polygraph instrument to record physiological measurements and interpret them according to specific protocols. These interpretations help in forming professional opinions about the potential deception of an examinee while answering relevant questions during the examination (Post Conviction of Sex Offenders and Polygraph Testing,
In the mental health field, there is currently no consensus on the reliability of polygraph evidence. The scientific community and state and federal courts hold contrasting views on this matter. Due to this lack of consensus, it is not justifiable to admit polygraph evidence. According to the American Polygraph Association, properly administered tests claim a 98% accuracy rate. However, challenges exist as test results have been proven manipulable, rendering them unreliable.

Polygraph tests are not admissible as evidence in 29 states. In six states, both the prosecution and defense must agree for polygraph test results to be considered admissible. However, New Mexico allows the use of polygraph tests. The federal courts have varying opinions on whether or not to permit polygraph evidence. Nonetheless, most federal courts have concluded, based on the US v. Scheffer case, that polygraphs should not be accepted as admissible evidence. It is important to acknowledge that until there is a consensus within the scientific community, the results of polygraph tests should not be considered admissible in court.

It is not recommended to use the polygraph test as a measure of probable cause or reasonable suspicion outside of court. Despite the replacement of the Frye standard by Daubert, there is no solid scientific foundation supporting the polygraph test. If the polygraph test were scientifically valid, scientists would have consensus on its accuracy. According to Daubert, courts must assess evidence’s relevance on a case-by-case basis; however, due to the potential inaccuracy of polygraph tests, they may be considered relevant but not reliable. Advancements in technology may lead more states to admit polygraph evidence in the future, but that time has not yet arrived.


The webpage titled “Conviction of Sex Offenders and Polygraph Testing” can be found at These references were last accessed on December 1, 2010: Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993), Frye v. United States, 54 App. D. C. 46, 293 F. 1013.No.3968,(1923), Rock v.Arkansas,483 U.S.44,55,Washingtonv.Texas,388 U.S14.,23,and Chambersv.Mississippi ,410U.S.,284 ,302-303 ,UnitedStatesv .Scheffer(1998).

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Should Polygraphs be used in Court Rooms as Admissible Evidence?. (2017, Feb 22). Retrieved from

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