In what situation might an investigator use a polygraph test?

An investigator might use a polygraph test to confirm the truthfulness of a witness's statement because polygraphs are designed to measure physiological responses that could indicate deception or truthfulness during questioning. This includes monitoring changes in heart rate, blood pressure, and respiratory patterns in response to specific questions. While the results of a polygraph test are often debated in terms of their admissibility in court and reliability, they can serve as a supplementary tool in an investigation. By applying a polygraph test to a witness, an investigator can gain insights into the credibility of the witness's statements, which can guide further inquiry and corroborate other evidence collected during the investigation.

Using a polygraph as the sole method of evidence collection, replacing all interviews, or utilizing it as an entertainment tool would not serve the investigator's purpose in gathering reliable and comprehensive information regarding the investigation.