How much does a private polygraph test cost? Trained polygraph examiners administer lie detector tests for a fee. The typical cost is between $200 and $2,000. The specific cost usually increases with the length of the test.

Use an Online Lie Detector Test There are some that are completely free to use, though the accuracy is questionable.

Lie detectors can be unreliable Some people will swear up and down that polygraph tests are very reliable. (Some of these people happen to be the ones who sell polygraph testing services.) Other sources indicate that the tests simply can't be counted on to return valid results.

Martin suggested that when conducted properly, polygraphs are correct 98% of the time, but no scientific evidence has been offered for this. The history of the polygraph is the subject of the documentary film The Lie Detector, which first aired on American Experience on January 3, 2023.