Before a polygraph test is conducted, a good interview is crucial in order to delve deeper into the cause of the problem. Knowing the subject who is going to take the polygraph test, the various situations in order to be able to better establish the types of questions to be asked.
The subject must sign a written voluntary consent form stating that he/she agrees to take a polygraph test, giving as much personal information as the polygraph technician requires, in terms of any illnesses he/she has had or has and whether he/she is taking any medication.
The staff of the centre may ask the subject to administer various tests, such as psychological tests, drug tests (in case of suspicion of drug use), check possible "countermeasures" that the subject has planned to try to adulterate his physiological reactions, etc...