For nearly a century, polygraphs have been a controversial tool in law enforcement and national security. Questioning a subject causes the device to measure changes in physiological signs. The theory is that deceptive answers will produce bodily responses that are detected. While polygraphs remain in use today, serious questions persist about their scientific validity and usefulness.
Debates around accuracy and admissibility
Despite the polygraph’s early acceptance, controversies emerged in the 1960s and 1970s over its scientific validity. Critics charged that polygraph testing relied on subjective interpretations of data rather than consistent physiological indicators of deception. In particular, academic psychologists challenged claims made about the polygraph’s accuracy. Meta-analyses found significant problems with false positives, false negatives, and inconclusive results. A general estimate of accuracy was at only around 60% in the best case. Several innocent subjects may have been misjudged as deceptive due to anxiety during the test. In the legal sphere, the polygraph faced scrutiny from state and federal courts. A major blow came in 1998 when the Supreme Court ruled against mandatory polygraph screening of public employees. Polygraph tests are generally inadmissible as evidence today due to doubts over scientific consensus on polygraph reliability.
Polygraphs still serve limited purposes in law enforcement and national security, despite their lack of scientific and legal validation. The lie detector test locations across USA conducts about 2-3 million tests per year. Cooperating witnesses or suspects may be polygraphed in criminal investigations. Tests require consent from both parties and results are not admissible in court. However, admissions or confessions during examinations provide investigative leads.
Federal agencies including the FBI, CIA, and NSA employ polygraph screening in applicant vetting and misconduct investigations. Privacy advocates have raised concerns over requiring the tests for government employment. There are also exemptions for undercover agents who must routinely lie. Within the national security realm, perhaps the most debated application is polygraph testing of scientists in sensitive roles. The Department of Energy began screening scientists and engineers with access to classified information about nuclear weapons in the 1950s. Critics argue this stifles research creativity and access to talent. However, government officials contend it is a necessary safeguard. Given longstanding issues around polygraphs, scientists have explored alternative biometrics and methodologies. But newer technologies also have downsides and unanswered questions.
One approach gaining traction in recent years involves functional magnetic resonance imaging (fMRI) of brain activity. Researchers identify regions like the prefrontal cortex that activate differently during deception. However, significant barriers exist, including high equipment costs and portability limitations. Like the polygraph, results may hinge on subjective interpretations. Some scientists say catching lies by examining physiological signs is the wrong approach entirely. They advocate techniques focused on emotional intelligence and interrogation tactics. By building rapport and watching for behavioral cues rather than monitoring blunt vitals, they believe trained investigators more accurately detect lies.