Why is the phrase “lie detector” misleading when describing a polygraph?

The term "lie detector" is misleading because a polygraph does not directly detect lies; rather, it measures involuntary physiological responses such as blood pressure, pulse rate, respiratory rate, and perspiration.12

These instruments are effective at recording nervous excitement, but they cannot definitively distinguish between the physiological markers of deception and those caused by other factors, such as anxiety or general nervousness. Because these reactions are not exclusive to lying, the test is susceptible to error and manipulation.12

Ethically, it is important to recognize that because these results can be influenced by emotional states rather than just truthfulness, relying on them as definitive proof of guilt or innocence is problematic. Consequently, the scientific community and judicial systems often view the polygraph with skepticism, limiting its admissibility in legal proceedings due to its inherent uncertainty.12