MICHAEL MARTIN: A polygraph is actually measuring an individual's fear of detection. That is what is making the test work because by understanding that there are penalties to being caught in the crime that they have committed, self defense mechanisms are activated and this is what we are recording with the exam. In some extreme cases, the chart may put lines off to the edge of paper and be extremely dramatic, but frankly most exams are very subtle and they require a trained eye to even tell the difference between the truthful and untruthful answers.

MICHAEL SPODAK: Although, I realize that it has its limitations in exactly ferreting out whether someone is being truthful it certainly tells you whether someone is being anxious.

BYRON WARNKEN: And we all carry a lot baggage up here from a lifetime of experience and so it may well be that for a bunch of reasons my results come back inconclusive.

MICHAEL MARTIN: Even though it is statistically reliable, it is not statistically infallible.

ANDY RADDING: They have been around for what 50 odd years. The courts have not become enamored of them.

ANDY RADDING: Polygraph evidence is not admissible at a trial unless both sides stipulate or agree that the polygraph will be admitted. You do not see that very often.

THE POLYGRAPH: WHAT'S IT GOOD FOR?

Polygraphs are routinely used in criminal and in some civil investigations. But they are rarely used as evidence in court.

As early as 1923, a federal appeals court precluded the introduction of polygraph evidence, finding in United States v. Frye that they were not generally accepted in the scientific community. While polygraph tests are commonly used in police investigations in the U.S., no defendant or witness can be forced to undergo the test.

Despite refinements to the test, judges have yet to recognize the test as sufficiently reliable to admit it into evidence at trials. Thus far, only one state, New Mexico, admits polygraph testing in front of juries under certain circumstances.

Sexual offenders are now routinely polygraphed in many states and it is often a mandatory condition of probation or parole. In Texas, a state appellate court has upheld the testing of sex offenders under community supervision and has also upheld written statements given by sex offenders if they have commited a further offense with new victims. These statements are then used when a motion is filed to revoke probation and the probationer may then be sentenced to prison for having violated his or her probation.

One federal law, known as the Employee Polygraph Protection Act prohibits most private employers from using lie detector tests, either for pre-employment screening or during the course of employment. Employers generally may not require or request any employee or job applicant to take a lie detector test, or discharge, discipline, or discriminate against an employee or job applicant for refusing to take a test or for exercising other rights under the Act. Employers may not use or inquire about the results of a lie detector test or discharge or discriminate against an employee or job applicant on the basis of the results of a test, or for filing a complaint, or for participating in a proceeding under the Act.

Subject to restrictions, the Act permits polygraph tests to be administered to certain job applicants of security service firms (armored car, alarm, and guard) and of pharmaceutical manufacturers, distributors and dispensers. Subject to restrictions, the Act also permits polygraph testing of certain employees of private firms who are reasonably suspected of involvement in a workplace incident (theft, embezzlement, etc.) that resulted in specific economic loss or injury to the employer.