Criminal Defense

Lie Detector Tests

February 09, 2018 by Anastasiia Ponomarova in Criminal Defense  
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Lie Detector Test, aka Polygraph Test

Defendants who have been accused of serious offenses often inquire about whether taking lie detector tests may help their case.

Experts disagree on how effective lie detector tests are. However, there are instances where a defendant under investigation for a criminal offense may actually want to take a polygraph test.

If you are considering taking a lie detector test, it is very important that you first consult with a Los Angeles Criminal Defense Attorney who has experience working with the best polygraph administrators and understands how best to handle it.

What is a Polygraph?

A polygraph, better known as a “lie-detector”, is a scientific instrument capable of simultaneously recording changes in several physiological parameters (blood pressure, pulse rate, respiration, electrocutaneous activity, etc.), while the subject is asked a number of questions related to a specific fact under investigation.

The records (or polygrams) obtained during the test are interpreted by a polygraph specialist.

What Does an Ordinary Polygraph Examination Include?

Professional polygraph examination consists of three phases:

  • Pre-test interview
  • Actual examination
  • Analysis of polygrams

The usual 3-part polygraph examination lasts 2-3 hours, and depends on the complexity and number of topics being investigated. The longest phase of the examination is a 45-90 minute pre-test interview. During the pre-test conversation, the polygraph examiner fills out the necessary documents and discusses the test questions so that the examinee fully understands every question before passing the survey.

The lie-detector specialist also explains the verification process on the lie detector and answers all questions of concern the subject may raise. The actual examination takes place in a quiet room with the doors closed in the presence of a polygraph examiner and the subject, without strangers, in order to prevent the influence of factors distracting the examinee.

The polygraph examiner fixes the necessary sensors on the body of the subject and prescribes preliminary discussed questions requiring a one-syllable answer – “yes” or “no.” Physiological indicators are recorded from the sensors of the lie detector in the form of “polygrams”. In the last phase of the polygraph examination, the polygraph specialist examines the polygrams and makes a conclusion about the veracity of the subject.

How are the results of the polygraph examinations used in court?

The results of checks on the lie detector are used as evidence in court in the United States. Most states, including California, allow the use of the results of polygraph checks as evidence, if the parties have agreed on their permissibility before conducting a polygraph examination, in accordance with the terms of the agreement.

  • The prosecutor, the accused and his defense counsel must conclude a written agreement that the accused will be subjected to a polygraph test and that subsequently the evidence of the test as well as the testimony of the test will be used in court.
  • In spite of the consent of the parties, the question of the admissibility of the results of tests on polygraph as evidence is ultimately decided by the judge who is considering the case. The judge’s negative attitude towards such evidence can be generated, for example, by a doubt in the competence of the operator, that conditions necessary for carrying out objective research were not met, etc.
  • The parties should have the right to subject the operator to cross-examination the following points: qualification and degree of operator’s preparedness; conditions under which the test was carried out; the disadvantages of this kind of tests and the possibility of error.
  • If the test results are admitted as judicial evidence, the judge reviewing the case must, in his parting words, draw the jury’s attention to the fact that the statements of the operator are aimed at establishing only the fact that at the time of the trial the accused was telling the truth or saying untruth, assess what kind of evidence should be given in this case to the results of a psychological study.

Can I cheat the Lie Detector Tests?

No, you can not cheat the lie detector tests. If you know that you are lying, the polygraph will definitely reveal a lie. Any qualified polygraph examiner who graduated from a polygraph training institution accredited by the ILPE and / or APA will undoubtedly reveal a lie. In addition, the computer polygraph approved by the ILPE has a phenomenal degree of accuracy reaching 100 percent, and is used in conjunction with ultra-efficient polygraph accessories that allow the polygraph examiner to identify countermeasures that a subject can resort to in an attempt to influence the result of a lie detector test.


There are several myths on the Internet that one can go through a polygraph, but none of the described ways can be called effective.

  • Not getting enough sleep
  • Drink alcohol
  • Pharmaceuticals
  • Caffeine, Excitement

If you are tired, yes, you will be calmer, but the polygraph can be calibrated for an organism with low reactions. Even if a person is tired, he or she will still give a reaction when you lie, usually.

If you drink a little, then the equipment will be calibrated. If you drink more, so that your consciousness becomes clouded, then you will be sent home, you will have to go through the polygraph again. Same with other drugs.

When is a Polygraph Test not Advised?

A polygraph is extremely bad to use when the questions are not asked in the native language of the subject. In particular, many polygraph specialists refuse to work with those who do not speak English well. The inner translation can sometimes cause unfavorable and confusing results.

Also, people who have mental health issues should avoid a Polygraph Test. Especially patients with schizophrenia who suffer from hallucinations and cannot distinguish the real world from the fictitious.

And lastly, “pathological liars”. They may actually in fact manage to pass or fail a polygraph by a method of auto-suggestion. They confuse their emotions much in the same way person with mental health issues might.

It’s best to consult a defense attorney to see if a polygraph test is a good strategy for your case.

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