Over the past century, polygraph tests, also known as lie detector tests, have been a controversial tool in law enforcement. A machine that monitors blood pressure, pulse, respiration, and skin conductivity monitors physiological changes caused by lying. Polygraph validity and reliability have been questioned since their introduction.
Why use tests of questionable accuracy?
From the beginning, there have been doubts about how accurately the polygraph detects lies. Early critics like William Moulton Marston noted that “lying, nervousness, fear makes your blood pressure go up”. Mistaken readings could implicate the innocent and allow the guilty to pass. It was found in a National Research Council report of 1997 that polygraphs are unreliable and susceptible to countermeasures. It is widely recognized that polygraph tests have little basis in science and psychology. Yet the polygraph persists. Polygraphs were almost universally used for personnel screening and criminal investigations by the 1960s. A million Americans were subjected to polygraph tests by the end of the 20th century. Why does reliance on this questionable device endure and even expand? Several factors perpetuate polygraph use:
- Cultural mythology – The polygraph is embedded in popular culture, portrayed in movies and TV as an infallible technology that gets at the objective truth. The mere presence of the machine elicits confessions. Belief in its powers remains strong despite scientific evidence to the contrary.
- Utility to law enforcement – While not admissible in court, law enforcement finds utility in the polygraph for guiding investigations, eliciting confessions, and pressuring criminal suspects. Polygraph confessions then lead to admissible evidence. The lie detector test locations across USA is useful even if not objectively accurate.
- Utility to government screening – Government agencies value polygraphs for screening applicants despite accuracy issues. Asking sensitive questions while connected to the machine deter admissions seen as disqualifying, even if Deception determinations are flawed. Agencies rely on mythology and intimidation factors.
- Lack of alternatives – While new technologies have been explored, none have replaced the polygraph as a lower-cost, portable, and “good enough” tool for its purpose. Better training, techniques, and instrumentation incrementally improve accuracy but are unlikely to catalyze its demise.
- Legal precedent – While polygraph results are not admissible as evidence, courts have not curtailed its use in investigations and screenings. Constitutional challenges have largely failed. Proponents argue its utility justifies its existence despite its flaws. Changing legal precedent is an uphill battle.
Paradox persists
The polygraph seems destined to remain a mainstay of law enforcement and national security procedures despite its shortcomings. The American public holds steadfast to the mythology and intimidation effect surrounding the device. New technologies have failed to displace their utility and cost-effectiveness for desired functions. And attempts at legal remedies have fallen short. The polygraph paradox persists, intertwined with our culture, institutions, and psyche – our desire to construct a machine that divines the truth.
