lie detector

A lie detector, or polygraph, measures physiological responses such as heart rate, blood pressure, breathing, and skin conductivity while a person answers questions. The premise is that deceptive answers may trigger subtle physical changes due to anxiety or stress. During the test, these responses are monitored and analyzed to determine whether a person is likely being truthful or deceptive. While not foolproof, polygraphs are often used in investigations as one tool among others to assess credibility, but their results are usually considered supplementary rather than definitive evidence in legal contexts.