Reasons for Failing a Lie Detector Test

1. THE EXAMINEE WAS LYING ABOUT THE TEST ISSUE

Obviously, if the Examinee was not being truthful to the test issues, that will result in a “deceptive” outcome. Some Examinees will continue to deny the allegation, and refuse to make any admissions, insisting that the result is incorrect.

2. THE EXAMINEE DID NOT DISCLOSE AN IMPORTANT DETAIL ABOUT THE TEST ISSUE, ALTHOUGH HE/SHE WAS MOSTLY BEING TRUTHFUL

If the Examinee was being mostly truthful to the test issues, but may have intentionally withheld a piece of information that could have been relevant to the investigation, this can cause a False Positive result. Some people may choose to withhold pertinent information because they are embarrassed, or don’t want to get in trouble for some related infraction.

3. THE EXAMINEE WAS UNCERTAIN ABOUT HIS/HER ANSWERS

If the Examinee was uncertain about his answers about the test issue due to vague memories or incapacitation (due to drugs, alcohol, or medications) at the time of the event in question.

For an Examinee to answer a question truthfully, that person must be certain of the answers. If the Examinee was under the influence of drugs, alcohol, medication, or sleep deprivation at the time of the event in question, that uncertainty can cause a False Positive result.

4. THE EXAMINEE DID NOT FULLY UNDERSTAND THE EXAMINER’S QUESTIONS ABOUT THE TEST ISSUE

If a cognitive, comprehension, or language issue resulted in a lack of clear understanding of the Examiner’s questions, that issue could cause a False Positive result.

5. THE EXAMINEE DID NOT FULLY UNDERSTAND THE EXAMINER’S EXPLANATION OF HOW THE TEST WORKS

Polygraph is a psychological procedure, not a medical exam. During this procedure, the Examiner must explain all about the exam, how it work, what to expect, etc. In order for the test to function correctly, the Examinee must fully understand the Examiner’s explanations and instructions.

6. THE EXAMINEE WAS ON MEDICATION THAT PREVENTED HIM/HER FROM FULLY UNDERSTANDING THE MEANING OR IMPORTANCE OF EVERY TEST QUESTION

If the Examinee is impaired in any way, that person may not fully understand the meaning and salience (importance) of each question asked during the procedure. Every question that the Examiner asks has a purpose, which is designed to elicit different types of physiological reactions. Failing to understand the reasoning behind every question can cause a False Positive result.

7. THE EXAMINEE ATTEMPTED COUNTERMEASURES

If the Examinee attempts to use methods to interfere with the test results, that attempt alone can create enough tell-tale markers to render the test “deceptive” even if the Examinee was being truthful. The profession is aware of individuals wishing to “augment” their exams by using methods to improve the test score, even though they are being truthful to begin with. Truthful Examinees should allow the exam to proceed normally, without attempting to alter the results.

8. THE EXAM QUESTIONS WERE POORLY DESIGNED BY THE EXAMINER

There are many rules for proper question design the Examiner must follow (see LINK for details). If these guidelines are not followed, the odds of a False Positive result will be increased due to poor question design.

9. THE EXAMINER USED A TESTING METHOD THAT HAS NOT BEEN VALIDATED BY SCIENTIFIC RESEARCH

APA validation standards are in place to ensure that a particular testing method meets or exceeds certain minimum validation standards. If an exam used a method that has not been validated by scientific research, the results will not be reliable. The result is an increased likelihood of a False Positive test result. Two such non-validated methods are the AMGQT and the R/I.

10. THE EXAMINEE DID NOT FOLLOW THE EXAMINER’S INSTRUCTIONS

For every polygraph, the Examiner will give the Examinee a number of instructions to follow during the procedure. If these instructions are not followed exactly, the data collected by the Examiner may be affected. An example would be the instruction to sit perfectly still, but some people may still nod or shake their head when they answer, or possible wiggle their fingers or tighten their muscles. Any distortions will affect the quality of data collected.

11. THE TEST RESULTS FELL INTO THE ALLOWABLE “ERROR RANGE”

Polygraph is about the probability of truthfulness, based on data collected and associated research. The best exam possible (single issue) may be as high as 93 to 95 percent accurate. However, that also means the test will produce incorrect outcomes 5 to 7 percent of the time, even if the exam is done perfectly. In other words, out of 100 truthful people taking the exam, 5 to 7 will still fail a properly administered exam, in spite of their truthfulness. Polygraph is not a perfect science, but it the best tool we have available at our current state of technology.

12. TOO MANY RELEVANT QUESTIONS WERE ASKED

In polygraph, the accuracy of the test decreases with the number of relevant questions asked. A single issue (one question) test is the most accurate, with a multiple issue (up to 4 questions) will be the least accurate. Asking more than four relevant questions in a test does not comply with APA test format validation standards, and these exam are considered “experimental,“ with accuracy rates approaching 50 percent (flipping a coin has the same accuracy). If more than one relevant question was asked in a test, the chances of an error are increased significantly.  The additional complexity is that if an Examinee “fails” one question in a multiple-issue test, they fail ALL of the questions on the test.  The proper protocol is not to make “split decisions” between the relevant questions (a person can not pass one question and fail another question, within the same exam).

13.  THE TEST WAS TOO SHORT

APA standards require an exam to last a minimum of 90 minutes.  This is to allow the Examiner to collect a sufficient amount of information during the pre-test interview, to allow the Examinee to become relatively comfortable with the process, to ask questions, to discuss all the test issues, and to provide clarifications as needed.  Most exams take 1.5 to 2.5 hours if they are done correctly.

14.  THE EXAMINEE WAS INTERROGATED BEFORE THE EXAM

If the person being tested was interrogated, questioned, or got in an argument, about the test issues on the same day as the exam, that person will likely fail the exam.  For this reason, APA standards of practice prohibit testing someone immediately following an interrogation or accusation.

15.  THE EXAMINER EXPRESSED BIAS DURING THE PRETEST INTERVIEW

The person being tested must trust that the examiner is impartial, and is only trying to get to the truth.  If the examiner indicates, in any way, that he/she believes the examinee is guilty, that trust is lost, and the exam is compromised.

16.  FATIGUE

If the person being tested has not slept for many hours prior to the exam, fatigue (sleepiness) will reduce the examinee’s ability to properly understand and process the questions being asked.  This can result in an erroneous test result.  This is why examiners require that the person get rest prior to the test.

17.  LOW BLOOD SUGAR

If the person being tested has not eaten for many hours prior to the exam, low glucose levels will affect the quality of data that is collected.  This is why examiners require that the person eat something prior to the test.

18. LACK OF FOCUS

If the person being tested is unable to focus their attention completely on the exam and the examiner’s instructions, the person may have reactions to issues that are unrelated to the test.  Examiners usually assume that reactions on the test are caused by the questions, but if the person being tested allows his/her mind to wander onto other issues, the examiner will assume those reactions are related to the test issues.  If a person submits to an exam while having more serious (distracting) issues on his/her mind, there is a significant chance of those thoughts interfering with the exam outcome.  Any person being tested must be prepared to give the examiner his/her full attention during the entire process, or risk erroneous results.