Effectiveness of the Polygraph
According to research, a well-trained examiner who uses the polygraph to detect deception can do it with relatively high accuracy. However, neither the polygraph nor the examiner is perfect. The interpretation would be subjective and the instrument is not foolproof.
Accuracy of the Polygraph Examination/Result
Studies on the accuracy of the polygraph test have been conducted over the last 75 years. It is difficult to draw a precise figure for the accuracy of polygraph testing in all settings from the data because many different factors are involved and the test itself is a very complex process. Nonetheless, the overwhelming body of evidence suggests that when a properly trained examiner employs a well-established testing procedure, the accuracy of the polygraph examiner’s decisions is generally in the range of 95%-100%, depending on the factors influencing the test.
Factors that Could Affect the Polygraph Examination
All empirical methods or scientific investigative methods are acknowledged and considered by the court during trial. As such, all experts doing any matter of lab work should be very careful to ensure that no data is contaminated.
The following are some of the factors that could influence the success or failure of a polygraph examination:
- Adequate examination facilities Before conducting an examination, the examiner should ensure that the instrument is in good working order, according to the manufacturer’s specifications, and will perform well during questioning. The attachments must be spotlessly clean and the examiner must properly explain how the instrument works and how it is used during the examination.
- Privacy must be assured The best ambiance for a polygraph examination would be a room that is away from noise or any form of disturbance. The examiner should make sure that no distractions will crop up during the conduct of the examination. This is to ensure that the subject is able to maintain their focus towards the test and to make sure that the subject could not make any disturbances an alibi or reason why there was a sudden change in their physiological reactions.
- Establishment of proper rapport between examiner and subject An effective examiner is one who can gain the subject’s trust and confidence, which can only be accomplished by establishing a good rapport or relationship between the examiner and the subject. Being a polygraph examiner is akin to being a psychologist in that you can direct the conversation and allow the subject to recognize you as an individual without any personal gain from the questioning. The examiner should make certain that the subject understands why the examination is being conducted.
- Reaching of the subject’s level of understanding There are various types of people who will be subjected to a polygraph examination. These different types of people will have their own level of understanding and perception on diverse topics. In order to better communicate and avoid offending the subject’s ego, the polygraph examiner should determine the type of personality and understanding that the subject possesses. The choice of words is crucial in ensuring that your point of view is not misunderstood by your audience.
- Permitting the subject to tell his side of the story The subject has the opportunity to speak and tell his own perception during the preliminary phase of the polygraph examination. During this time, the examiner should allow the subject to speak and share his side of the story or version of the story in order to boost the subject’s confidence and reduce their anxiety. Examinees who are intimidated by the examiner are more jittery and reactive. Allowing them to speak has an advantage for the examiner in that the subject’s statements can be used as a basis for question formulation, especially in preparation for the main polygraph examination phase.
- The subject of the examination Physical and mental capabilities, past associations, economic and educational status, employment, background, sensitivity to right or wrong, and the subject’s personal projection should all be taken into account by the polygraph examiner when formulating the questions to be asked during the examination.
- Chart interpretation The ability of the polygraph examiner to interpret polygrams following the examination is another factor to consider. He must be able to distinguish between responses that contain or do not contain deception criteria. He must be completely familiar with the chart markings of guilty potentials and collusion potentials, as well as consequences that will befall the guilty subject.
- The examiner Among all the variables that could influence the test results, the polygraph examiner, or the person who administers the test, must be given careful consideration. The examiner must be in good physical and mental health, as well as being a professional examiner. He must be familiar with the examiner’s techniques and approaches to the examination process. If the examiner is ineffective in his work, the results may be contaminated or no accurate results will be obtained.
The Ideal Polygraph Examination Room
When conducting a polygraph examination, the examiner must be careful to consider the following setup so as not to affect or hinder the success of the examination:
- A room that is free from vehicular and human traffic and preferably on the ground floor
- Must be conveniently ventilated or air-conditioned
- Must be conveniently-sized with an adjoining observer room equipped with a one-way mirror, microphone, tape recorder, and amplifier
- Must be soundproof and acoustic
- Must have an outlet of 110 volts to 60 cycles
- Color must not be glaring to the eyes, blue or plain white will do
- Must not possess any telephone, decorated picture frames, ornamentals, etc.
- Must have a system to indicate whether a room is occupied
- Must only have one door
Factors Affecting the Validity of the Polygraph
Generally, the following factors affect the accuracy of the polygraph exam:
- the instrument itself
- condition of the subject
- condition of the examination room
- the qualification and skills of the examiner
Specifically, about 15% of errors in the polygraph exam are said to come from the following:
- nervousness or extreme emotional tension experienced by a subject who is telling the truth regarding the offense in question but is nevertheless affected by apprehensions, over-anxiety, even anger
- physiological abnormalities
- mental abnormalities
- attempts to “beat the machine”; and,
- unobserved behaviors of the subject