The polygraph test

In the polygraph test we seek the truth and to achieve it it is necessary to follow a few steps, each and every one more or just as important as the previous one.

The interview

The polygraph test

Before the polygraph test, a good interview must be carried out, it is crucial in order to delve into the cause of the problem. Know the subject who is going to pass the polygraph test, the various situations in order to better establish the types of questions that are going to be asked.

The subject must sign a voluntary consent letter stating that they agree to pass the polygraph test, detailing how much personal data the polygraph technician requires, regarding diseases they have had or have and if they take medication.

The center staff may request the subject to administer various tests, such as psychological tests, drug tests (in case of suspicion of consumption), review possible “countermeasures”, that the subject has planned to try to adulterate their physiological reactions , etc…

Elaboration of the questions

Once the questions to be asked are agreed, normally between a number of not less than 3 and not more than 5, of each type of question: relevant, control or irrelevant, being of two types:



With which you want to evaluate the sincerity of the subject in his answer, control that are those questions in which a highly suggestive reaction of the subject is expected, due to shame, fear, etc. and is expected to want to lie in it.


of control

The control questions are those where it is intended to generate an intense emotional and physiological reaction in the subject, in order to be able to compare it with the physiological reactions established in the relevant questions.



Which do not cause any reaction in the subject to be evaluated. All the questions are loaded into the polygraph software, establishing different series with a different order in the questions, the sensors and electrodes are connected to the polygraph, and to the computer.

test preparation

The polygraph test

The posture of the subject before the polygraph test is important when performing the test, they must be barefoot, with their feet flush with the wall, wearing comfortable clothing and without accessories that may bother or oppress the recording of sensors and electrodes. .

He must be facing the wall, at a neutral plane, without stimulation, since sometimes his pupil dilation can be controlled, as well as his gestures and micro-expressions recorded.

Once seated, they are asked to sit on the recording pad, which evaluates the subject’s motor response. Once located, the plates that evaluate resistance are placed on intercalated fingers, which, together with electrodes placed on the same hand, that measure conductance, a complete galvanic record of skin perspiration will be obtained.

Subsequently, place the pleistesmograph , on the back of the thumb of the same hand, to assess blood volume, which together with the cuff located above the crease of the arm, about 2-3 cm, with the manometer at a pressure of 60 mmHg, to see the cardiac response of the individual.

The proof

The polygraph test

Once the instrument has been calibrated, the technician proceeds to carry out the polygraph test with the questions in series, not less than 3, following the various orders of established agreed questions.

Moments before starting the polygraph test, the subject is asked to take 2 seconds to answer each question asked by the technician, not to move, while possible gestures are observed, such as clearing the throat, sighing, inhaling, etc. .. and should the technician write down in the polygraph software.

Between each series, at least a 5-minute interval is left, where the subject is asked to clarify any anomaly, behavior, that may have occurred, such as changing an answer to a question from Yes to No, or from No. So.
At the end of the test, the electrodes and sensors are removed in the reverse order in which they were put on.

Final Result and Conclusions

The polygraph test

Once the polygraph test is over, the subject is asked to leave the room, so that the technician can assess, with the help of the software’s logarithm, the probability of truth or falsity of the subject in each question.

The technician who performed the polygraph test will compare the physiological reactions that have been obtained from the subject in the different control and relevant questions, in order to determine if the answers to the relevant questions are significantly higher or lower.

After the polygraph test, it is necessary to carry out a detailed analysis, in which the gestures and actions that the subject may have done when answering these questions must also be taken into account.

If the results are clear, the technician meets again with the interested parties to communicate the results, after paying for the service.

the polygraph

The polygraph test in Malaga

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The report

The communication of results is a delicate moment, since there is a lot of expectation to know the conclusions.

The report can be oral, with cordial treatment, and pedagogical, explaining in each question the probability of its veracity.

The conclusions to each question should be illustrated and explained with the graphs of the answers to each of them.

The polygraph test report is not a fundamental requirement, but it is important to have the entire polygraph test process in writing and have a record for future reference.

other possibilities

Sometimes an interpreter may be required, since knowing the language and its compliments is very important when it comes to fine-tuning when preparing questions, understanding the subject, the causes, etc… Therefore, the service will require of this supplement.

When the technician considers that it is necessary to carry out another type of test, such as psychological, personality, or drugs, it will also have an increase, depending on the test.

In some situations there are different subjects who must take the test, such as for a job interview, or in a case of job or family mistrust… In these cases, depending on the volume, a supplement will be set for each person to take the test.

In very exceptional situations, it may happen that the results are not entirely clear, so it would be possible either to repeat the test, or to have to postpone the communication of results for the near future.

If at any time during the test, it is perceived that the subject to be examined deliberately tries to manipulate the results of the test, it is automatically stopped and reflected in the report, since the subject previously signed the voluntariness of the test. conducting the test.

Other information of interest about the polygraph or lie detector according to Wikipedia, if you are interested in hiring our services, do not hesitate to contact us or if you have doubts or questions about the polygraph test.

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