New Lie Detector May Find Its Way to Court

By: Gerri L. Elder

Prosecutors are generally not allowed to use the results of lie detector tests in criminal court as evidence against defendants. Now, however, criminal defense attorneys in San Diego are creating a controversy by attempting to submit the results of a new type of lie detector test as evidence. The test, they say, proves their client is not lying.

Lawyers hope to have an fMRI scan admitted as evidence in a juvenile sex abuse case. The fMRI measures brain activity based on oxygen levels. Its developer, No Lie MRI, claims the test is 90 percent accurate at detecting lies.

The technology used by No Lie MRI is widely used in brain research. However, it has not been fully tested in the realm of lie detection. Lawyers may have a problem having the results of the test admitted as evidence, as it has not yet been generally accepted among the scientific community. Some scientists and lawyers are still skeptical about the technology’s ability to detect lies.

The accuracy of lie detector tests has always been questionable. The polygraph was invented in 1921 and has been studied in depth ever since. Lie detector tests are still not generally admissible in criminal court, with few exceptions. Except by agreement among the lawyers involved in a case, lie detector tests are inadmissible in court in every state except New Mexico.

In 1973 in State v. Dorsey, the New Mexico Supreme Court found that polygraph tests are admissible as long as three requirements are met. The polygraph operator must be competent, the procedure must be reliable and the tests on the subject must be valid.

Then in 1983, the New Mexico legislature passed the Rule of Evidence law allowing polygraph evidence to be admitted as evidence at the judge’s discretion if all requirements were met. The specific requirements of admissible polygraph evidence in the state then became:

  • The polygraph must be conducted by a person who is qualified as an expert polygraph examiner
  • The polygraph must be quantitatively scored in a manner that is generally accepted as reliable
  • Prior to conducting the polygraph, the polygraph examiner must be briefed on the subject’s health and educational background and any other relevant information
  • At least two relevant questions must be asked during the polygraph examination
  • At least three charts must be taken of the subject

No other state has enacted a similar law to allow polygraph evidence in court, although there have been many studies done and scientific papers written purporting its accuracy.

It has been 88 years since the invention of the polygraph and it is still not widely accepted as evidence in criminal cases. The fMRI may have a long road ahead before being accepted by the scientific community at large and the courts. However, with new developments in science and technology, lie detector evidence may eventually find its way into the criminal court system. Scientifically proven lie detector evidence could become a powerful tool for criminal lawyers and prosecutors alike, and has the potential to change the face of the criminal justice system.