When most people hear of a lie detector test, they tend to think the machine is capable of telling when someone is lying or not. While this holds true in some circles, the technology has its fair share of critics. According to the co-creator of Antipolygragh.org, George Maschke, “The public needs to know that polygraph testing has no scientific basis and is inherently biased against truthful people, yet liars can train themselves to pass”.

 

On An Interview With Business Insider

Maschke went further to dispute the lie detector machine on the ground that its results are dependent on the takers ability to tell a lie on certain control questions. Private investigators ask control questions which include questions one would tag as harmless enough to admit to. Such questions include, “have you ever taken office supplies home?” or “have you ever told a lie to get out of a problem?”

Maschke, in his defence, continues by saying if takers of the test are able to focus their thoughts on something else during the test, it becomes a whole lot easier to pass the test. Lie detectors work my reading three main indication markers;

  • Blood pressure and heart rate – pressure is taken through an arm cuff
  • Sweat – readings are taken with the electrodes attached to the fingers
  • Breathing – gotten through chest straps

A combination of these markers gives an impression on a graph by creating up and down lines that rise and fall. With these statistics, private investigators are able to tell if the taker is lying or telling the truth.

 

President Of The American Polygraph Association

So further clarify the principle of the machine, Raymond Nelson, President of the American Polygraph Association, told Business Insider that the common name “lie detector” is a name used out of sheer convenience and not necessarily because of science. In simple terms, this is because polygraph machines do not measure lies. According to Nelson, the polygraph only records how well people are truthful to relevant and control questions and how deceptive they do to same. The difference in the response to these types of question is what private investigators use to tell when one is lying or being truthful.

 

Analysing Polygraph Questions

Nelson agrees that analysing polygraph questions is not as easy as one thinks. Private investigators compare answers of control questions with those of relevant questions. For instance, this is the same procedure a professor at a university would use to track students’ progress. He would conduct tests at the beginning of the school year (control questions) and at the end (relevant questions) to determine the difference.

Polygraphs have found their use in criminal investigations and are slowly gaining acceptance in government agencies. These agencies hire private investigators to help out in application processes.

Nelson told the NPR that the use of the polygraph “…still better than any other technology today”. It puts the tests accuracy above 80% mark. Even with the criticism that trails it, lie detectors still find their use and remain legal and state and federal levels.