FAQ

The recommended range is between 3 and 6 questions, to ensure maximum reliability of the test.

A polygraph test takes between 60 and 120 minutes, and the full appointment between 2 and 3 hours, depending on the complexity of the case and the number of topics to be assessed. That time is not just the moment with the sensors: the recording session itself takes about 45 to 90 minutes, but the service includes three phases. First, the pre-test interview, in which the examinee's state (rest, medication, anxiety) and each of the questions are reviewed and agreed in advance —nothing is asked by surprise—. Then the test, in which each series of questions is asked at least three times to contrast the answers. And finally, the analysis of the charts and the preparation of the report, which the examiner carries out after the appointment. That is why it is best to set aside the morning or the afternoon and come without rushing: reliability depends on doing each phase well.

The reliability of a polygraph test with validated techniques and an accredited examiner is around 85-90%; it is not 100%. The American Polygraph Association reports an aggregate accuracy of 87% (range 80-94%) combining the validated techniques, rising to 89% in single-issue tests, and the National Academies of Sciences review (2003) estimated around 89% in field studies. That figure is not automatic: it depends on the examiner's training and accreditation, on how the questions are framed and on the examinee's state (rest, medication, anxiety). That is why the result is interpreted as supporting evidence, never as an infallible verdict. At El Polígrafo we work with a strict protocol, a calibrated Stoelting CPS Pro system and expert analysis of the charts to place ourselves at the high end of that range.

The questions have to be answered with YES/ NO, and they have to be specific, spatially and temporally. You can bring your questions, and we will help you shape them for maximum reliability.

The evidence is voluntary and can therefore be proposed by the Security Forces and Corps, by the Honourable Member or even by the person under investigation.

A polygraph test is a test that measures the body's physiological responses to determine whether or not someone is being honest in answering specific questions.

A polygraph works by measuring variations in blood pressure, heart rate, respiration, skin conductance and skin reactance while the examinee is asked questions.

The main components of a polygraph include sensors to measure blood pressure, heart rate, respiration and skin conductance.

During a polygraph test In order to assess the physiological responses of the examinee, control questions, relevant questions and irrelevant questions are asked.

Polygraph tests are carried out by an accredited examiner (polygrapher), not just any technician. At El Polígrafo, the test is led by an examiner with training accredited by the European Polygraph Association, a Doctor of Psychology from the University of Malaga and a forensic psychologist registered with the Official College of Psychologists of Eastern Andalusia. That dual competence —psychology and polygraphy— is key, because the machine does not run the test: the examiner designs the questionnaire, conducts the pre-test interview, fits the sensors, asks the questions and, above all, interprets the charts and prepares the report. The examiner's training and accreditation are the factor that most influences the reliability of the result. That is why you should always check the qualifications and experience of whoever is going to carry out the test, and be wary of anyone who cannot prove them. The whole process is carried out with confidentiality and the examinee's consent.

A polygraph examiner should combine three things: specific, accredited training in polygraphy, a solid grounding in psychology or psychophysiology, and practical experience conducting exams. The reference accreditation in Europe is granted by the European Polygraph Association; there are also training programmes such as those of the European Polygraph Academy. To that it is worth adding a university degree in Psychology and, when the test is used in the expert-witness field, the status of registered forensic psychologist. The examiner at El Polígrafo holds training accredited by the European Polygraph Association, a doctorate in Psychology from the University of Malaga and registration with the Official College of Psychologists of Eastern Andalusia. These credentials matter because the reliability of the test depends directly on who runs it: the same equipment, in unqualified hands, gives unreliable results. Before hiring, always ask to be shown the examiner's qualifications and accreditation.

Yes, it is necessary to complete specific training at a recognised polygraph school and obtain certification to become a polygraph examiner.

The tests of polygraphs are used in criminal investigations The following are some of the most common situations in which the truthfulness of claims needs to be verified: pre-employment assessments, internal investigations, and in personal situations.

Fooling a polygraph is very hard and, with an accredited examiner, unlikely, though it is not mathematically impossible. There are so-called countermeasures —controlling breathing, tensing muscles, doing mental arithmetic or causing oneself pain— with which some people try to alter their physiological responses. The problem for whoever tries is that those manoeuvres leave their own trace on the charts: a trained examiner recognises them as artefacts and as a pattern of attempted manipulation. In addition, the polygraph records three signals at once (breathing, cardiovascular activity and the galvanic skin response) and each series of questions is repeated at least three times, which makes it very costly to keep a deception consistent across all of them. That is why reliability depends so much on the examiner's skill: the machine is not enough, you need someone who knows how to read the records and detect the inconsistencies.

The accuracy of a polygraph test depends above all on four factors: the examiner's training and accreditation, the examinee's physical and emotional state, how the questions are framed and the presence of medication or substances in the body. These elements make the difference between the low end (around 80%) and the high end (close to 90%) of the accuracy range reported by reference associations such as the American Polygraph Association. Rest, anxiety, certain drugs (anxiolytics, stimulants) or some medical and psychological conditions can alter physiological responses; that is why the pre-test interview reviews sleep, medication and the examinee's state before fitting the sensors. The questions are agreed in advance and each series is asked at least three times to contrast the answers and rule out one-off reactions. During the analysis, artefacts such as coughs or micro-movements are also controlled for.

If someone disagrees with the results, they can request a review of the data by another certified examiner or take another test with a different examiner.

Prior to the test, the examiner informs the examinee about the process, obtains consent and conducts an interview to gather relevant information and establish a set of questions.

Prohibited questions vary by jurisdiction, but generally include those that violate privacy, discriminatory questions, or those unrelated to the purpose of the test.

Yes, a person can refuse to take a polygraph test, but the consequences of refusal depend on the context in which the test is requested.

Polygraph tests are generally safe and non-invasive, but may cause anxiety or stress in some people.

A person's rights during a polygraph test include the right to be informed about the process, to give consent, to stop the test at any time and, in some cases, to ask for a review of the results.

The examiner analyses the physiological responses recorded during the test with the help of the polygraph software, which has a complicated system of algorithms to determine whether there are indications of deception or sincerity in the answers to the relevant questions.

In Spain, the results of a polygraph test are not admitted as evidence in criminal proceedings: the courts do not grant them probative value to determine guilt or innocence. The Supreme Court has repeatedly rejected the polygraph as a means of evidence in criminal proceedings, because it measures physiological reactions —not the truth itself— and its result is not conclusive. Its real usefulness is out of court: clearing up doubts in the private, couple or corporate sphere, always with the person's consent. In that context, the examiner delivers an expert report with the charts, the scoring and the conclusions in terms of probability, which can provide guiding information to the parties, but it never replaces the judge's assessment nor turns the polygraph into judicial evidence. If you are looking for evidence with criminal value, the polygraph is not the right tool.

A standard polygraph test in Malaga costs €350, and includes the pre-test interview and the test. Services with an expert report for judicial use range from €500 (expert report) to €1,000 (expert and psychological report, with ratification and defence of the report in court). Each additional person tested on the same day is €100 more, up to a maximum of ten people per day. To book, a €50 deposit is paid, which is deducted from the final price. The amount does not change according to the result —it costs the same whatever the outcome, as a guarantee of impartiality— nor is it charged per question. What can vary the quote is the number of topics to be assessed, the type of report and whether the test is carried out at our premises or requires travel; in that case it is always stated in advance. You can see the full breakdown on the pricing page.

Yes, you can request a test of polygraph for personal use However, it is important to bear in mind the limitations and accuracy of the test.

There are other techniques for lie detection such as body language analysis, voice assessment and facial expression analysis, although none of these are infallible.

A polygraph is an instrument used to carry out lie detection tests, while a lie detector is a generic term that can refer to different techniques or devices used to determine whether or not someone is being honest, including the polygraph .

When selecting a polygraph examiner, consider his or her experience, certification, reputation, cost and communication skills.

To prepare for a polygraph test, the most important thing is to arrive rested, without substances that alter physiological responses and with a cooperative attitude. Sleep well the night before, avoid alcohol and drugs, and go easy on caffeine on the day of the appointment. If you take regular medication (for example, anxiolytics, antidepressants or blood-pressure medication), do not stop it on your own: tell the examiner, who will take it into account when interpreting the results. You do not need to memorise anything or rehearse answers: in the pre-test interview the whole process is explained to you and the questions to be asked are reviewed one by one, so that none catches you by surprise. Eat something light so you do not come on an empty stomach, and arrive in good time so you are not stressed. In short: rest, honesty about your medication and calm; the protocol takes care of the rest.

If someone has a medical or psychological condition that could affect the results, it is important to inform the examiner before the test so that he/she can take the necessary precautions and evaluate whether the test is appropriate.

It is, of course, a test of veracity of testimony, used as a supplement to authenticity in pleadings, especially when there is no evidence other than the statements themselves.

In Spain there is no specific law regulating the use of the polygraph. The test is carried out in the private sphere and always voluntarily: it requires the person's informed, written consent, and they can refuse or stop it at any time. It is not a test admitted in criminal proceedings —Spanish courts do not grant it probative value to determine guilt or innocence—, so its use is out of court: clearing up doubts in the personal, couple or corporate sphere. The physiological data it records and the result are personal data, so their processing is subject to data-protection law (GDPR and the Spanish LOPDGDD): they are collected with consent, for a specific purpose and with confidentiality. In short: there is no regulation specific to the polygraph, but there is a framework of consent and data protection that governs its private, voluntary use.

You can find out more about testing for polygraph and its applications through of professional polygraph organisations, accredited polygraph schools and online resources dedicated to the subject.