The use of so-called “lie detectors” to solve crimes and gain convictions has been largely overstated by the media and the big screen. As a matter of fact, many states don’t allow the results of a polygraph test to be admitted in court at all. The fact is, they are unreliable. Their unreliability is widely recognized by criminal justice professionals (aside from the polygraph administrators) but police agencies continue to use them.
Polygraph machines work by measuring certain physical qualities and responses, namely patterns in your heart rate. As questions are read, the test administrator analyzes these patterns and reportedly determines whether you are being honest or not. But despite what these analysts would have you believe, it’s not an exact science.
Doubts to the reliability of these tests are nothing new. It’s these doubts that have resulted in several states (New York, Illinois, Pennsylvania, D.C.) not allowing polygraph test results to be admitted in court at all. Other states including California, Arizona, Florida, and Georgia, allow the results to be used both only if everyone agrees to them and with different disclosures being required about their fallibility.
A recent investigative report from McClatchy has found additional problems with polygraph testing—in the equipment itself. One particular machine is said to be delivering inaccurate results and “glitches” that cause some measurements to change completely.
Despite all of this, some police agencies use the tools during the investigative phase of the test—even in states where the results would be inadmissible under the rules of evidence. And the reason isn’t to determine whether or not you are lying, but to draw a confession out of you.
According to the McClatchy investigation:
Despite the scientific skepticism, intelligence and law enforcement agencies see polygraph as useful in obtaining confessions to wrongdoing that wouldn’t otherwise be uncovered. Fifteen federal agencies and many police departments across the country rely on polygraph testing to help make hiring or firing decisions. Sex offenders and other felons often undergo testing to comply with probation or court-ordered psychological treatment. Police detectives and prosecutors rule out criminal suspects who pass and scrutinize those who don’t.
“We’re talking about using a procedure that has a very weak scientific foundation and making it worse,” said William Iacono, a University of Minnesota psychology professor and polygraph expert. “I already don’t have very much confidence in how government agencies conduct these tests. Now, they might as well be flipping a coin.”
Like intimidating good cop- bad cop tactics and placing you in an interrogation room alone far longer than necessary, the use of polygraph tests can largely be seen as a psychological tool in police work. The good news is, you don’t have to take one.
When you are questioned about a crime, long before they suggest a polygraph, you can exercise your right to have an attorney present. Police departments know how to get in your head; they’ve been doing this for decades. You need someone with the same sort of knowledge working on your side.
About David Matson