Polygraph how is it used in a criminal proceeding?

Polygraph tests, often referred to as “lie detector tests,” do not really detect lying but rather they monitor the physical reactions of the participant, namely the sweat or galvanic skin response, heart rate, and blood pressure. As fluctuations for any of these factors changes, a needle within the machine rises and falls. Polygraph examiners then analyze the patterns to make a determination on the probability that the participant is telling the truth or lying.

Critics of polygraph tests, including Raymond Nelson, president of the American Polygraph Association, argue the test results do not really detect lying but rather that the “polygraph test measures the differences between how truthful people react to relevant questions and control questions and how deceptive people react to those questions.”

More specifically, the examiner is trying to determine how someone would react to a relevant question when compared to their reaction to the control question. Critics also point out that the stress from the test itself could make the results of the polygraph test inclusive.

Supporters of the polygraph test have concluded; however, that even the best liars would have difficulty controlling all three components measured by the test. Other supporters would argue that many criminals who are actually guilty of a crime would not voluntarily submit to a polygraph test unless they were convinced they knew how to “beat the test.”

Are polygraphs or detectors used in court?

Although there are no states which require alleged criminals to take a polygraph test, some law enforcement agencies will attempt to get someone who has been arrested for a crime to voluntarily submit to a polygraph test.

What should you do if you have been arrested for a crime? If you have been arrested and have been asked to take a polygraph test it’s important to know your rights. Talk to a criminal attorney before taking the test to find out if it will benefit your criminal case. Additionally, even if you submit to the polygraph test and pass the test, there is no guarantee that this will convince the state that you are innocent.

For example, some individuals who have been arrested for a crime and refused to take a polygraph test have found that the police were even more convinced of their guilt.

Know your state’s laws for polygraph testing

As mentioned above, you may not be forced to take a polygraph test. States do, however, have different strategies for dealing with testing results. For example, some states have decided the polygraph is too unreliable and do not allow the results of the test to be used as evidence in a criminal court case.

In the State of Texas, for instance, polygraph examinations are not admissible in criminal court by either the prosecution or the defense. According to the Texas courts, the results of the polygraph test are too unreliable to be considered as evidence in a criminal case.

Other states such as California, however, do allow results of polygraph tests to be included as evidence in a criminal trial, arguing that the jury can make their own determination about a defendant’s innocence or guilt after reviewing the results of a polygraph test.

Bottom line:

Whether or not you should take a polygraph test or whether you will be allowed to present the results from a polygraph test as evidence in your case will depend on the laws of your state. You should not, however, take a polygraph test without first consulting with your criminal defense lawyer.