Know the law about polygraph accuracy and admissibility

In Law School For You, learn the law about the polygraph: OJ Simpson failed, and Jon Benet Ramsey's parents passed. The police can't make you take one, but the CIA can. So what good is it?

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WASHINGTON, June 11, 2017 ⏤ Depending on the results, police, criminal defendants, employers and employees either love or hate the polygraph.

Also called a “lie detector,” the polygraph’s name has Greek roots and means “many writings.” It does not detect lies. It measures and records several body responses such as blood pressure, pulse, respiration and skin conductivity while a subject is asked and answers a series of questions. The belief is that deceptive answers will produce responses that notably vary from the responses of a person who is truthful.

Humans lie. The search for proof of truth has been and remains a vaunted and elusive effort. In ancient China, dried rice was placed in a person’s mouth and when they spat the rice out, they were considered guilty if they still had rice sticking to their tongue. Innocents were believed to be able to produce saliva, enabling them to spit the rice out, whereas guilty people had “dry mouth.”

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In 1921, John Larson, a University of California medical student, invented the modern polygraph. Today the machine is more sophisticated but uses the same basic concepts: measuring and recording the body’s responses to questions.

The scientific and legal communities have provided opinions about the effectiveness of the polygraph. Psychologists have also commented on its use.

In 1991, a survey of scientists overwhelmingly (66 percent) determined that polygraphy was fake science. In 2002 the National Research Council found that in “untrained” populations, polygraph tests can distinguish lying from truth telling at rates well above chance, but well below perfection. Thus, with psychologists repeatedly declaring that the tests were unsound, the NRC stated in 2004 that there was no evidence of the test’s effectiveness.

Polygraph advocates claim that test results are valid in up to ninety percent of tests administered.

Use in criminal courts

The United States Supreme Court addressed the admissibility of polygraph test results in 1998, when they stated that “there is simply no consensus that polygraph evidence is reliable.”

In the case United States v. Scheffer, polygraph evidence in a military tribunal was excluded because, as the Court noted, “false positives occur, and these people suffer the consequences of ‘failing’ the polygraph.” Further “the polygraph examiner can supply the jury only with another opinion.” The court said that the test was “no more accurate than a coin flip.”

The court said that the test was “no more accurate than a coin flip.”

Polygraph evidence is not admissible in a criminal court to prove a defendant’s guilt or innocence. In some states, however, if there is an agreement between both sides (prosecution and defense) before the test is taken, the results can be admitted into court as evidence.

Nonetheless, police and prosecutors use the test extensively to elicit confessions, and criminal defense attorneys attempt to use them as leverage in plea bargains.

A criminal defendant cannot be forced to undergo the test.

John and Patsy Ramsey, the parents of the murdered six-year-old Jon Benet Ramsey voluntarily took polygraphs to clear their names in the investigation of their daughter’s death. They passed the tests. This crime was the subject of national attention and many now believe one or both of the parents were somehow involved.

This crime was the subject of national attention and many now believe one or both of the parents were somehow involved.

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OJ Simpson failed a lie detector test over his involvement in killing his former wife, Nicole Brown, and her friend, Ron Goldman. Based in part on those results, and other evidence, a civil jury awarded his victim’s families millions in compensation.

Gary Leon Ridgway (the 1980’s “Green River” killer) pled guilty to the murders of 48 women after being linked by DNA evidence. He was suspected of having killed at least 70 victims. He passed a polygraph in the midst of his spree in 1984.

He passed a polygraph in the midst of his spree in 1984.

Polygraph tests measure emotional arousal. Anxiety, anxiety disorders such as post-traumatic stress, nervousness, fear, confusion, hypoglycemia, psychosis, depression, substance-induced changes in “normal” or other emotions can all lead to errors if polygraph test results are interpreted as deceptive. A polygraph cannot distinguish anxiety caused by dishonesty and anxiety caused by something else.

A polygraph cannot distinguish anxiety caused by dishonesty and anxiety caused by something else.

As many know, police lie. They are allowed to do so in attempting to extract confessions. As well, where a defendant has agreed to take a polygraph, the police have been seen to lie to the defendant about the results in order to get the confession. After intense and lengthy interrogations, some defendants caved when they were confronted with “you failed the test,” believing they had no hope and that they’d fare better confessing than being found guilty.

Police may tell a suspect that the test is mandatory to prove innocence. That is simply not true. The test is never required.

Use in employment arena

In the employment world, polygraphs are used in a variety of ways. Prior to 1988, employers routinely used the polygraph for pre-employment screening and after-hire job continuation determinations. In 1988, the federal Employee Polygraph Protection Act was passed. The Act outlawed significant uses of lie detectors in connection with employment.

The Act applies to every private employer involved in interstate commerce, which today includes just about every business. Those using a computer, the U.S. mail, or a telephone system to send or receive messages in states other than their own are included.

Under the Act, it is illegal to:

  • Require, request, suggest or cause any employee or job applicant to submit to a lie detector test;
  • Use, accept, refer to or inquire about the results of any test conducted on an employee or job applicant;
  • Dismiss, discipline, discriminate against or even threaten action against any employee or job applicant who refuses to take a test; and
  • Discriminate against or fire any who claim the Act’s protections.

The EPPA does allow polygraph testing for certain types of jobs, such as those with security firms (armored car employees, alarm companies, guard companies), and for jobs with pharmaceutical manufacturers, distributors, and dispensers.

Further, if an employer is investigating a specific employment-related crime, upon 48-hour written notice to an employee that the employee is a suspect, taking the test can be required for continuation of employment. There must be a provable, reasonable suspicion that the employee was involved in the crime.

The EPPA does not cover federal, state or local government agencies. Government employees do not have the protection of this law.

In the realm of government or government-related employment, a security clearance cannot be revoked based solely on polygraph test results. Access to sensitive information, however, may be denied if results are not favorable. Finally, some security-type government positions require passing the test, and failure can mean being denied such a position.

Employees who choose to take a test have rights concerning the test and its administration. There are topics that cannot be asked about, including religion, sexual preference, race, labor union activity and lawful political activity.

An explanation of what the test results will be used for, the right to stop the test at any time, and the right to be asked questions in a way that is not degrading or needlessly intrusive are also attendant to a voluntary taking of the test.

Keeping your fingers crossed behind your back does not otherwise permit lying.

Paul A. Samakow is an attorney licensed in Maryland and Virginia, and has been practicing since 1980.  He represents injury victims and routinely battles insurance companies and big businesses that will not accept full responsibility for the harms and losses they cause. He can be reached at any time by calling 1-866-SAMAKOW (1-866-726-2569), via email, or through his website

His book “The 8 Critical Things Your Auto Accident Attorney Won’t Tell You” can be instantly downloaded, for free, on his website:

Samakow has now also started a small business consulting firm. The website for this business is brand new and Mr. Samakow will be most appreciative of any and all comments.

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Paul Samakow
Attorney Paul Samakow brings his legal expertise and analysis from the trenches of the courtroom to Communities Digital News. A native Washingtonian, Samakow has been a Plaintiff’s trial lawyer since 1980 practicing in the DC metro area. Paul can be reached at any time by calling 1-866-SAMAKOW (1-866-726-2569), via email @ [email protected], or through his website @ He is also available to speak to your group on numerous legal topics.