A polygraph (or „lie detector”), commonly known as a „lie detector,” is a device that examines unconscious bodily reactions. Contrary to popular belief, this device does not detect lies, but allows for the determination of whether a person possesses memories (memory traces) related to a specific event. Its use in Polish criminal proceedings for the purpose of making factual determinations is permitted only in certain cases and always requires the consent of the person being examined.
Above all, it is important to remember that the Code of Criminal Procedure explicitly prohibits the use of a polygraph and other means intended to control unconscious bodily reactions of the person being questioned in connection with an interrogation (Article 171 § 5 item 2 of the Code of Criminal Procedure). Therefore, the lawful use of this device is only possible outside of an interrogation.
Pursuant to Article 192a, a polygraph examination, with the consent of the person being examined, may be administered by an expert to limit the circle of suspects or to determine the evidentiary value of the evidence found. However, it should be remembered that information obtained in this manner can only constitute supporting evidence, meaning it cannot be the sole evidence of a crime in a case in which a conviction is being issued. However, Article 199a permits the use of a polygraph as part of an examination conducted by an expert, also with the consent of the person being examined.
