A lie detector test , officially known as a polygraph test, measures and records several physiological indicators while a subject answers questions, to determine truthfulness. The theory behind the lie detector test is that deceptive answers will produce physiological responses that can be differentiated from those associated with non-deceptive answers. Typically used in criminal investigations, employee screenings, and personal disputes, a lie detector test can be a useful tool, though it’s not without controversy regarding its accuracy. The lie detector test , while popular, is not universally accepted in legal contexts due to potential errors. Lie detector tests are conducted by trained professionals who analyze the results to assess the truthfulness of the subject’s responses.