Polygraphs have been a subject of controversy in the legal and scientific communities for decades. These tests have been widely used in criminal investigations and national security vetting to help determine whether an individual is being truthful.
The tests measure physiological responses—such as heart rate and skin conductivity—to determine whether an individual is being deceptive. However, while these tests are often depicted as reliable truth-detection tools, their actual accuracy and admissibility in criminal investigations remain debatable.
The accuracy and reliability of polygraphs
Some factors that can determine the accuracy of polygraph tests include:
- The skill of the examiner
- The physiological state of the subject
- The testing method used
Proponents argue that polygraphs are highly accurate, while critics contend that the error rates are too high for polygraphs to be considered reliable forensic tools. Potential inaccuracies can arise from these tests due to false positives. This happens when a truthful person experiences high levels of anxiety during the test.
False negatives can also arise when a deceptive person is clever enough to remain calm and composed while they give false responses. Sometimes, results can be compromised due to examiner bias because polygraph results require human interpretation.
Should polygraphs be used in criminal investigations?
While polygraphs may be useful as an investigative tool, relying on them as primary evidence in criminal investigations is problematic. Given their susceptibility to inaccuracies and manipulation, they should not serve as a standalone determinant of guilt or innocence.
Fortunately, courts do not accept lie detector test results as evidence during the hearing of a criminal case. The Supreme Court ruled that the results are unreliable, so defendants need not worry about polygraphs having a major influence on criminal proceedings.
Until polygraph technology advances to achieve near-perfect accuracy, its role in criminal investigations should be approached with caution. Defendants undergoing investigation should enlist legal support to help ensure they understand their related rights accordingly.