The polygraph, also known as a lie detector tool, is an instrument that measures and records various physiological responses such as blood pressure, pulse, breathing, breathing rhythms, body temperature and electrical conductivity of a subject´s skin when answering a series of questions on the specific basis that false answers produce differentiated measurements that can be measured and quantified by an algorithm.

This machine measures the physiological changes caused by the sympathetic nervous system during interrogation. Within the U.S federal government, a polygraph test is also known as a Psychophisiological Detection of Deception (PDD) exam. Here´s how we test the polygraph, describing all of its steps:

To carry out a Testimony Credibility Assesment through the application of the polygraph, a methodological process based on an international standard or standard defined by the International ASTM E-52 Committee / American Standard for Testing and Materials must be followed, indicating the conditions and minimum time that must be devoted to the test to obtain reliable results.

Signature of consent document is required, where the examinee agrees in writing, agreeing to be asked about a specific matter, further indicating who can know the results and conclusions of that assesment.

The test is carried out in a private and confidential environment, without the presence of third parties, except when the assitance of a translator or interpreter is needed. However, in domestic cases and for particular reasons a witness may be present, usually the couple. Before the test began, customers should have turned off their mobile pones, avoiding interruptions

The place where the polygraphic test is carried out shall have suitable environmental conditions, absence of noise or other sensory stimuli that could cause distractions to the person undergoing the test, altering the recording of the test graphs.

It is important that the examiner has adequate and sufficient information on the matter to be dealt with, so that he can build the interview and the test questions. A standard polygraph test has a minimum duration of 90′, being usual to last two or more hours depending on the complexity of the case.

Far from typical police or judicial interrogations, the examiner will use a non-aggressive method to obtain the subject’s information, trying to obtain his full version of the facts. In this regard, the polygraph’s questions will focus on the events in which the subject is alleged to have been able to participate, so that the veracity of his testimony can be determined by relevant and direct questions.

The test begins with an informative interview that values the suitability and physical and psychological conditions of the subject, who must be in normal health conditions, having rested adequately, without being affected by disease processes that undermine his physiological and/or cognitive abilities, in order to obtain acceptable neurophysiological response values.

Although is not a mandatory step, it is common for the examiner to explain to the examinee how the polygraph works, that is, how the instrument is able to perform accurate measurements and how they are recorded on a chart that will then be valued by a sophisticated algorithm created based on data collected from thousands of previous polygraphic tests, accrediting, depending on the technique used, a reliability that ranges between 92 and 98%.

The recording of audio or video of the total or partial development of the sessions contracted by the client is not allowed. Exceptionally, and depending on the special circumstances, the tests may be recorded in audio and video, with the consent of the person evaluated, provided that for reasons of quality of service this type of support must be added in expert opinions for courts, always guaranteeing confidentiality. A urine test may also be required prior to the start of the session in order to rule out chemical countermeasures.

Once the questions have been defined, the examiner will proceed to read them aloud, ensuring that the examinee fully understands them, who will respond with a “YES” or a “NO” to each of them, recording the questions and the answers below in the polygraph program.

The questions and answers are recorded in the polygraph program, then the person being evaluated is invited to sit in a special chair, where they will be asked to relax and answer the test questions without make any type of movement or body gesture, so that the graph only collects the responses to the stimulus caused by the question, without being altered by unnecessary motor activity.

Modern digital polygraphy equipment consists of up to twelve channels, being necessary to have at least the following:
Two pneumographs, which measure respiratory activity at the thoracic and abdominal level, will be the first to install on the examinee. Next, the band that measures the heart rate is installed on the arm and then on the index and ring fingers two strips that measure the variations in sweating / EDA or electro-dermal activity of the skin. Finally, the plethysmograph is installed on the little finger, which measures the pulse at the peripheral level.

The examinee sits on a special chair that contains at its base a motor activity sensor, also known as “countermeasures”. Some teams have sensors of this type in the armrests and under the feet, all to rule out attempts to manipulate the test by the examinee.

The questions are presented in several batches, randomly, to prevent the subject from predicting the order of the questions and producing unnecessary stimuli. The way in which the test is performed is at the discretion of the examiner or polygraph operator, always maintaining control of it in order to obtain the most reliable results.

The test concludes with the analysis of the graphs and obtaining the results in an automated way, 05. Although the final decision is made by the examiner who will manually perform a numerical quantification of the graphs before rendering a written report. For a higher quality of our services, at Poligrafo.com we perform a double assessment of cases where deception has been identified in the responses. In these cases, the graphs are analysed by another expert on the team, in order to obtain a qualified second opinion that confirms the final result.

The data of our exams remain stored for a minimum of three years, being during that time protected by encryption codes and stored in a cloud, being able to be deleted at any time at the request of the client.

The necessary hygienic measures will be observed at all times, following the advice and regulations of the health authorities, with special emphasis on the situation arising from the crisis caused by Covid-19, maintaining the minimum necessary distance between the participants, as well as the use of masks and hydroalcoholic gel.

Contracting services: Poligrafo.com offers professional services throughout Spain, with variable rates depending on the type of matter to be dealt with, the location where the service is required and the datesrequested. Guarantee: It is usual to require a deposit of 50% or more of the budget of the service in order to be able to cover travel expenses and ensure the commitment acquired by the client. The deposit is only reimbursed in the event that Poligrafo.com cannot carry out the provision of the service due to force majeure beyond its control.

This information note is not a contractual document and cannot be interpreted as such. Clients may express their doubts or obtain more information about the service by writing to info@poligrafo.com